TN 


Le 


IC-NRLF 


77    flfil 


]  v;  '"'- 


REESE  LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 

^eceiveJ  crttsu.  ,  180  ff. 

cAc cessions  No.  6fJ~/J     .     Class  No. 


*  NOTES 


Metallurgical  Analysis 


ARRANGED  FOR  STUDENTS  IN  THE  METALLURGICAL  LABORATORY 
OF  THE  OHIO  STATE  "UNIVERSITY. 


BY 

NATHANIEL  W.  LORD,  E.  M 

PROFESSOR    OF    MINING    AND    METALLURGY. 


COLUMBUS,  OHIO. 
1893. 


COPYRIGHT    1893,  BY   NATHANIEL   W.  LORD. 


PRESS    OF    HANN    &.    AOAIR,  COLUMBUS,  O. 


PREFACE. 


STISHESE  notes  were  written  for  the  use  of  the  writer's 
students  in  the  metallurgical  laboratory  of  the  Ohio 
State  University. 

The  object  was  to  give  in  a  condensed  form  the  series 
of  selected  methods  in  metallurgical  analysis  which  made 
up  the  course  of  study. 

To  the  descriptions  of  the  processes,  such  explanations 
have  been  added  as  experience  has  shown  to  be  desirable  for 
the  assistance  of  the  student  in  understanding  the  conditions 
necessary  for  accurate  results. 

Such  methods  only  are  given  as  have  been  tested  by 
repeated  use  in  the  laboratory  and  found  satisfactory. 

No  attempt  is  made  to  describe  general  reagents  or  ap- 
paratus, as  students  prepared  to  take  this  course  are  always 
familiar  with  all  ordinary  laboratory  equipment  and  for 
special  forms  of  apparatus  reference  is  made  to  easily  access- 
ible books  and  papers. 

The  writer  wishes  to  acknowledge  his  obligation  to 
Blair,  Troilius  and  other  standard  writers,  as  well  as  to  num- 
erous papers  in  the  various  technical  and  scientific  journals, 
though  it  has  been  impossible  to  give  credit  in  detail  to  all 
the  sources  from  which  material  was  taken  in  compiling 
these  notes. 

The  references  added  are  only  those  which  it  seemed 
important  the  student  should  consult  for  fuller  information 
on  the  subject. 

October  28,  1893. 


CONTENTS. 


PAGE 

Introduction 5 

Obtaining  and  Preparing  Samples  for  Analysis  7 

The  Analysis  of  Limestones 10 

The,  Determination  of  Iron  in  Ores 1 5 

The  Determination  of  Phosphorus  in  Iron,  Steel,  and  Iron  Ores., ...  20 

The  Determination  of  Silicon  in  Iron- .. . . •  .*. .  35 

The  Determination  of  Manganese -. 38 

The  Determination,  of  Sulphur , ............  ,50j 

The  Determination  of  Carbon  in>  Pig  Iron  arid  Steel I . .  59 

The  Determination  of  Titanium  in  Iron  Ores. 68 

The  Analysis  of  Coal  and  Coke  ... 73 

The  Analysis  of  Furnace  and  Flue  Gas , . . 79 

T*he  Analysis  of  Blast  Furnace  Slag .'. 83 

The  Analysis  of  Fire  Clays  . . ... .;....... 85 

The  Determination  of  Copper  in  Ores >. .  .88 

The  Assay  of  Ores  for  Zinc 91 

The  Analysis  of  Alloys  of  Lead,  Antimony,  Tin  and  Copper ; . . .  93 

The  Examination  of  Water  for  Boiler  Supply . ....-.-' .-..-. . . .  96 

APPENDIX. 

Table  of  Atomic  Weights 98 

Table  of  Factor  Weights. 99 

Applying  Correction  Factors  of  Volumetric  Solutions  to  the  amounts 

of  Substance  taken. 9i3 

Some  additional  Notes  and  Methods .100 

1.  Sampling  Spiegel  Iron  and  White  Cast  Iron. ..... ....... .100 

2.  The  Determination  of  Iron  in  Ores  by  Permanganate. . . . .  100 

3.  On  Difficulty  in  Filtering  Solutions  of  Pig  Iron  and  Steel  in 

Phosphorus  Determinations 100 

4.  The  Purification  of  Barium  Sulphate. .. '. 101 

5.  On  the  Presence  of  Nitrites  in  Caustic  Alkalies  as  a  Source 

of  Error  in  Sulphur  and  Carbon  ^Determinations 101 

Errata  . .  . .  102 


INTRODUCTION. 


EFORE  beginning  the  course  in  special  analysis  given 
in  these  notes,  the  student  is  supposed  to  be  familiar 
with  the  ordinary  qualitative  reactions  of  the  acids  and 
bases,  the  preparation  of  reagents,  and  so  much  of  the 
general  methods  of  quantitative  analysis  as  includes  the  use 
of  the  balance  and  weights,  the  ordinary  operations  of  fil- 
tration, washing,  drying,  igniting  and  weighing  of  precipi- 
tates, the  evaporation  of  solutions,  and  also  the  use  and 
calibration  of  graduated  glassware. 

A  careful  study  of  the  first  two  sections  of  Fresenius' 
System  of  Quantitative  Analysis  will  be  found  of  the  utmost 
importance  in  regard  to  all  these  points  of  manipulation. 

In  addition  to  the  above  a  few  general  precautions  and 
explanations  are  necessary  and  should  never  be  overlooked. 

In  adding  reagents  to  produce  any  given  effect  it  is 
important  that  the  right  amount  be  used.  What  this  will 
be  demands  a  thorough  knowledge  of  what  is  to  take  place. 
In  the  descriptions  of  the  various  processes  these  amounts 
are  approximately  indicated,  but  it  is  impossible  to  provide 
in  this  way  for  all  contingencies.  Therefore,  if  the  amount 
of  reagent  directed  fails  to  do  the  work  it  must  be  increased 
or  diminished  as  may  appear  necessary.  Thus  in  every 
case  where  a  precipitate  is  formed,  it  is  essential  that  the 
filtrate  be  tested  by  a  further  addition  of  the  reagent  to 
make  sure  that  the  precipitation  is  complete.  This  is  best 
done  by  adding  the  reagent  to  a  small  portion  of  the  liquid 
in  a  test  tube,  and  if  a  precipitate  forms  returning  this  to 
the  main  volume ;  often  a  little  of  the  clear  liquid  over  the 
precipitate  can  be  tested  in  this  way  before  filtration. 

In  all  careful  work  the  chemicals  used  should  be  tested 
as  to  purity.  Many  of  the  so-called  u  C.  P."  reagents  are 

(v) 


vi  Introduction. 

unreliable.  A  "  blank  "  determination  serves  in  many  cases 
to  detect  this  source  of  error.  This  is  made  by  going 
through  the  process  with  the  reagents  alone,  leaving  out  the 
substance  to  be  tested.  The  amount  of  any  impurity  which 
would  affect  the  result  is  thus  determined  and  can  be 
allowed  for. 

In  testing  a  process  it  is  always  desirable,  as  was  sug- 
gested by  Dr.  Wilson,  to  make  duplicates,  using  different 
amounts  of  the  substance.  Agreement  of  results  under 
these  circumstances  is  obviously  a  much  better  guarantee  of 
accuracy  than  when  the  same  amount  is  used  in  each  case. 

The  amounts  of  material  prescribed  in  the  description 
of  the  processes  are  those  most  generally  used.  They  may 
be  changed  provided  the  reagents  be  varied  to  correspond. 

A  useful  modification  of  many  processes  consists  in  the 
use  of  u  factor  weights."  That  is,  weighing  out  an  amount 
of  the  substance  equal  to  some  multiple  of  the  percentage 
which  the  element  to  be  determined  makes  of  the  precipi- 
tate weighed.  Thus  the  actual  weight  will  represent  the 
percentage,  and  all  calculation  be  avoided. 

A  table  is  added  to  these  notes  giving  a  series  of  such 
weights  which  may  be  substituted  for  those  usually  taken. 

The  same  method  may  frequently  be  used  to  avoid  the 
application  of  a  factor  of  correction  in  the  case  of  standard 
volumetric  solutions. 


NOTES  ON  METALLURGICAL  ANALYSIS. 


OBTAIXIXti     AXI)      PREPARING     SAIUPUES     FOR 

ANALYSIS. 

The  object  sought  by  the  technical  analyst  is  to  ascer- 
tain correctly  the  average  composition  of  some  certain  lot  of 
material  —  for  example,  a  car  load  of  ore. 

The  amount  of  material  treated  in  the  laboratory  is  of 
necessity  limited  to  a  few  grammes. 

The  proper  preparation  of  this  small  portion,  that  its 
analysis  shall  correctly  represent  the  composition  of  the 
mass  from  which  it  is  taken,  constitutes  the  operation  of 
"sampling" 

The  general  mode  of  procedure  is  to  take  from  the  mass 
in  question  a  large  amount  selected  from  different  points, 
and  containing  coarse  and  fine  material  in  the  same  propor- 
tion as  they  exist  in  the  mass  as  a  whole.  This  large  sample 
which  may  weigh  from  200  pounds  to  a  ton,  according  to  the 
amount  of  material  the  chemist  has  to  examine,  as  well  as  to 
the  extent  of  variation  permissible  in  results,  is  then  crushed 
to  one-half  inch  or  smaller,  thoroughly  mixed  and  sub- 
divided by  "quartering,"  until  a  sample  of  about  ten  pounds 
is  obtained ;  this  is  pulverized  and  all  put  through  a  6-mesh 
sieve,  well  mixed  and  again  subdivided,  till  a  sample  of  100  or 
200  grammes  is  obtained,  which  is  put  through  a  90-mesh 
sieve  and  bottled  for  use. 

Many  variations  will  be  necessary  with  different  mater- 
ial. The  following  general  principles  may  be  stated  : 

1.  As  to  size  of  original  large  sample.  This  must  be  greater  as 
the  material  is  less  homogeneous  and  as  the  importance  of  the  exact  de- 
termination of  any  ingredient  increases.  Thus,  a  limestone  can  be 

(7) 


8  Notes  on  Metallurgical  Analysis. 

easily  sampled ;  but  a  gold  or  silver  ore  consisting  of  small,  detached 
fragments  of  a  very  valuable  material  in  a  valueless  rock  may  require 
the  fine  crushing  of  the  whole  mass  of  ore  and  its  careful  mixing  and 
subdivision,  to  secure  an  "average  assay." 

2.  Materials  of  decidedly  different  specific  gravities  require  great 
care  to  prevent  separation  into  layers  during  mixing.     "Quartering," 
that  is,  division  of  the  flattened  pile  into  quarters  and  then  the  sepa- 
rating of  one  of  them,  all  of  which  must  be  carefully  brushed  together, 
constitutes  a  fair  safeguard  against  this  source  of  error. 

3.  Every  particle  of  any  portion  must  go  through  the  sieve.   The 
harder  parts  which  are  left  unbroken  toward  the  last,  are  of  different 
composition  from  the  softer  and   first  pulverized  portions,  and  if  re- 
jected would  cause  serious  error. 

4.  Certain  ores  and  slags  contain  particles  of  metal  which  can- 
not be  pulverized.    These  must  be  kept  by  themselves,  and  the  weight 
of  the  particles  taken;  also  the  weight  of  the  portion  of  the  sample 
passing  through  the  sieve.    The  metal  is  then  analyzed  separately  from 
the  siftings,  the  two  analyses  combined  in  the  ratio  of  the  relative 
weights. 

Ihe  sampling  of  metals  presents  many  difficulties.  Melted  metals 
can  be  sampled  during  pouring  by  taking  a  little  at  the  beginning, 
middle  and  end  of  the  cast,  and  averaging  the  three  analyses. 

In  general  it  may  be  stated— 

1.  Cast  ingots  are  not  homogeneous.    Drilling  from  different  por- 
tions will  show  different  analyses.    Hence,  drillings  from  a  number  of 
points  must  be  well  mixed.    A  single  "pig"  of  cast  iron  may  vary 
largely  from  top  to  bottom. 

2.  In  tapping  a  mass  of  metal  from  a  furnace  different  portions 
of  the  "  run  "  will  show  different  compositions.    Thus,  a  "  bed"  of  pig 
iron  will  show  wide  variations  in  silicon  and  sulphur  between  the  top 
and  bottom  of  the  cast. 

3.  In  some  metals  the  operation  of  drilling  will  result  in  a  sepa- 
ration ;  for  example,  in  drilling  pig  iron,  the  fine  portion  will  be  of  dif- 
ferent composition  from  the  coarser ;  hence,  careful  mixing  of  the  drill- 
ings is  necessary. 

'^VEIGHING  OUT  "   FROM  THE  LABORATORY  SAMPLE. 

In  this  operation  the  tendency  of  material  of*  different  specific 
gravities  to  separate  must  never  be  lost  sight  of.  The  substance  should 
be  carefully  mixed  together  upon  a  sheet  of  glazed  paper  and  small  por- 
tions taken  from  different  parts. 

A  second  source  of  error  is  the  separation  of  "  coarse  and  fine,"  as 
in  metal  drillings.  Great  care  is  necessary  to  avoid  serious  difficulty 
here.  The  drillings  may  be  moistened  with  alcohol  so  as  to  become  ad- 


Notes  on  Metallurgical  Analysis.  9 

herent  and  then  small  portions  may  be  separated,  to  be  subsequently 
( when  dry)  accurately  weighed  (Shimer). 

The  machinery  for  sampling  may  be  quite  elaborate. 
References  on  methods  of  and  machinery  for  sampling— 

A.  A.  Blair  — The  chem.  anal,  of  iron,  2d  Ed.,  pp.  1-18  ;  also  p.  199. 
Jour.  an.  and  app.  chem..  vol.  V,  p.  299  —  sampling  iron  ores. 
Jour.  an.  and  app.  chem.,  vol.  II,  p.  148  —  as  to  irregularity  of  pig  iron. 
Eng.  and  Min.  Jour.,  1892,  p.  75 —  sampling  machine. 

P.  W.  Shimer,  sampling  cast  iron  borings,  Trans.  Inst.  Min.  Engs.,  vol.  XIV,  p.  760. 
Win.  Glenn,  sampling  ores,  Trans.  Inst.  Min.  Engs.,  vol.  XX,  p.  155. 

H.  L.  Benjamin,  sampling  machine,  and  also  illustration  of  hand  sampling,  Trans.  Inst.  Min. 
Eng.,  vol.  XX,  p.  416. 

E.  K.  Landis,  iron  ore  sampling,  Trans.  Inst.  Min.  Engs.,  vol.  XX,  p.  611. 

ESTIMATION   OF   MOISTURE. 

Many  materials  as  sampled  in  bulk  are  quite  damp. 
Such  ( ores,  clays,  limestones,  etc. )  must  be  dried  in  a  steam 
bath  or  by  other  means,  and  the  loss  of  weight  determined. 
This  drying  is  best  done  on  a  portion  of  one  or  two  pounds 
of  the  crushed  and  mixed  material,  which,  after  drying,  is 
pulverized  for  the  final  sample.  It  is  always  well  to  deter- 
mine moisture  also  in  the  final  sample,  and  allow  for  it  if 
present.  The  temperature  for  drying  must  not  exceed 
100°C. 

The  analysis  may  be  stated  on  the  "  dry  basis  "  and  also 
calculated  on  the  wet  material. 

For  example :  From  a  car  load  of  iron  ore  portions 
were  taken  at  different  points,  being  careful  to  take  proper 
amounts  of  lump  and  fine.  The  amount  taken  was  200 
pounds.  This  was  broken  up  as  fine  as  beans,  well  mixed 
by  shoveling  and  divided  by  quartering  until  a  portion  of  two 
pounds  was  obtained,  all  being  done  rapidly  to  avoid  loss  of 
moisture. 

This  portion  was  weighed  on  an  ore  scales. 

Weight 925.4  grms. 

After  drying  in  a  pan  on    a  steam 

boiler  —  weight 864.9  grms. 

Loss 60.5  grms. 


10  Notes  on  Metallurgical  Analysis. 

This  was  then  pulverized,  mixed  and  a  portion  of  100 
grms.  taken  for  the  laboratory.  This  assayed — 

Iron 58. 4  per  cent. 

Then  925.4  :  864.9  =  58.4 :  X  =  the  per  cent,  of  iron  in 
the  ore  in  bulk. 

It  may  be  noted,  1st,  that  many  ores  will  absorb  water  during  pul- 
verization. The  water  so  absorbed  will  vary  with  the  weather ;  2d,  com- 
plete drying  of  a  large  sample  is  very  difficult ;  3d,  ordinary  corked  bot- 
tles are  not  moisture  proof,  and  samples  left  in  such  will  change  in  the 
course  of  time. 

When  much  work  is  done  special  ovens  for  drying  samples  are  of 
great  assistance.  For  description  of  one  used  at  the  Edgar-Thomson 
Steel  Works,  see  Blair  chem.  anal,  of  iron,  p.  200. 

TUB    ANALYSIS    OF    I^IIWBSTONBS. 

The  materials  to  be  determined  are  "  The  insoluble  silicious  mat- 
ter," consisting  of  sand  (silica)  and  insoluble  silicates,  principally  clay. 
Oxides  of  iron  and  alumina,  usually  not  separated  when  small  in 
amount,  carbonate  of  lime  and  carbonate  of  magnesia.  The  iron  is 
sometimes  present  as  ferrous  carbonate. 

In  examining  limestone  quarries  to  determine  the  quality  of  the 
stone  for  furnace  flux,  lime  or  cement  manufacture,  the  rock  should  be 
sampled  layer  by  layer  as,  different  layers  usually  vary  greatly  from 
each  other  in  composition,  while  material  from  the  same  layer  (or 
"bed"  )  is  likely  to  be  of  moderately  uniform  composition.  The  stone 
generally  ranks  in  quality  according  to  the  amount  of  carbonate  of  lime. 

Process  of  Analysis. — Weigh  1  grm.  of  the  finely  ground 
sample.  Transfer  it  to  a  4-in.  caserole  or  dish,  cover  with  a 
watch  glass,  add  25  to  30cc  of  H2O,  then  15cc  cone.  HCL, 
warm  until  all  effervescence  has  ceased,  remove  the  cover, 
wash  it  off  into  the  dish,  add  4  or  5  drops  of  HNO3  and 
evaporate  the  solution  to  dryness  on  a  water  bath  or  hot 
plate,  or  replace  the  cover  and  boil  down  directly  over  the 
lamp,  using  constant  care  to  prevent  loss  by  u  spattering ;" 
finally  heat  carefully  over  the  lamp  flame  until  all  odor  of 
HC1  is  gone  and  the  CaCl2  just  begins  to  fuse;  now  cool,  add 
5cc  of  HC1,  warm  till  the  Fe  salts  are  dissolved,  add  50cc 
H2O,  heat  until  everything  dissolves  except  the  silicious 
matter,  which  forms  a  flocculent  or  sandy  residue,  filter 


Notes  on  Metallurgical  Analysis.  11 

through  a  5  or  7  c.  m.  filter,  wash  thoroughly  with  hot  water 
until  a  few  drops  of  the  washings  show  no  reaction  for  Cl 
when  tested  with  Ag  NO3. 

Ignite  and  weigh  the  residue,  which,  after  deducting  the 
weight  of  the  filter  ash,  constitutes  the  "  insoluble  silicious 
matter,''  keep  it  for  the  determination  of  the  silica  by  fusion. 

To  the  filtrate,  which  should  be  about  lOOcc,  add  NH4 
HO  until  it  just  smells  distinctly  of  NH3,  should  the  precip- 
itate be  light  colored  and  large  in  amount,  add  5cc  HC1  and 
again  NH4HO  as  before,  now  boil  the  liquid  until  the  smell 
of  NH3  has  nearly  gone  —  maintaining  the  volume  of  the 
liquid  by  adding  water  from  time  to  time.  Now  remove 
the  lamp,  and  let  the  precipitate  settle,  filter  into  a  small  fil- 
ter and  wash  well  with  hot  water,  ignite  and  weigh  the  pre- 
cipitate of,  Fe2  O3+A12  O3. 

The  Fe2O3  may  be  determined  in  another  portion  and 
when  deducted  from  the  above  will  give  the  alumina  by 
difference. 

Dilute  the  filtrate  to  about  200cc,  heat  to  boiling  and 
add  40cc  of  a  saturated  solution  of  (NH4)2  C2O4  first  diluted 
with  40cc  of  water  and  heated  to  boiling  also.  Stir  well,  and 
let  stand  until  the  precipitate  of  CaC2O4  has  completely  set- 
tled, decant  the  liquid  through  a  9  c.  m.  filter  without  dis- 
turbing the  precipitate,  wash  the  precipitate  once  or  twice 
by  decantation,  using  about  lOOcc  of  boiling  water  each 
time,  then  transfer  to  it  the  filter  and  wash  6  or  7  times  with 
hot  water. 

Dry  the  precipitate  thoroughly,  detach  it  as  far  as  pos- 
sible from  the  filter,  put  it  in  a  weighed  No.  0,  porcelain 
crucible,  burn  the  filter  carefully  on  a  platinum  wire  and  add 
the  ash  to  the  contents  of  the  crucible,  now  drop  cone.  H2 
SO4  on  to  the  precipitate  till  it  is  well  moistened,  but  avoid 
much  excess.  Heat  the  crucible  (working  under  a  "  hood  " 
to  carry  off  the  fumes)  holding  the  burner  in  the  hand  and 
applying  the  flame  cautiously  until  the  swelling  of  the  mass 
subsides  and  the  excess  of  H2SO4  has  been  driven  off  as  white 


12  Notes  on  Metallurgical  Analysis. 

fumes,  finally  heat  to  a  cherry  red  for  5  minutes.  Do  not  use 
the  blast  lamp !  Cool  and  weigh  the  CaSO4.  The  weight  of 
the  CaSO4  multiplied  by  0.735  gives  the  amount  of  Ca  CO3 
in  the  sample.  The  filtrate  from  the  CaC2O4  should  be,  if 
necessary,  concentrated  by  boiling  to  300cc  ;  should  any  Mg 
C2O4  separate,  dissolve  it  by  adding  a  little  HC1.  Cool,  add 
NH4HO  till  alkaline,  then  add  lOcc  or  a  sufficient  quantity  of 
a  saturated  solution  of  Na2HPO4  then  add  gradually  -^  of  the 
volume  of  the  liquid  of  strong  (26°)  NH4HO,  stir  hard  for 
some  time,  cover  and  let  settle  until  the  liquid  is  perfectly 
clear  (about  2  hours),  filter  and  wash  with  water  containing 
TV  of  its  volume  of  strong  NH4HO  and  a  little  NH4NO3,  dry, 
detach  from  the  filter  and  burn  the  filter  on  a  platinum 
wire ;  now  ignite  precipitate  and  filter  ash  in  a  porcelain  cru- 
cible, using  the  blast  lamp  for  10  minutes. 

The  ignited  precipitate  is  Mg2P2O7  which  multiplied  by 
0.756  gives  the  MgCO3  in  the  sample. 

Treatment  of  the  Silicious  Residue  for  the  Determination 
of  SiO2. — Mix  the  ignited  residue  with  8  or  10  times  its 
weight  of  dry  Na2CO3,  put  the  mixture  in  a  platinum  crucible 
of  15cc  or  more  capacity,  heat  it  over  a  Bunsen  burner  until 
the  mass  has  caked  together  well,  then  over  a  blast  lamp 
until  it  is  in  quiet  fusion,  now  remove  the  crucible  with  a 
pair  of  tongs  and  dip  the  bottom  in  cold  water,  which  will 
frequently  cause  the  mass  to  loosen. 

Wash  off  any  of  the  material  spattered  on  the  cover  of  the 
crucible  into  a  caserole  with  hot  water,  add  the  fused  cake,  if 
it  has  come  loose  ;  if  not,  fill  the  crucible  with  water  and  warm 
until  the  fused  mass  softens  up  and  can  be  transferred  to  the 
caserole,  finally  clean  the  crucible  with  hot  water  and  add 
the  washings,  if  any  material  adheres  so  as  not  to  be  removed 
by  washing,  dissolve  it  with  a  little  HC1  and  add  to  the  rest, 
(on  no  account  punch  or  "dig"  the  crucible  out).  When 
the  fusion  has  been  thoroughly  disintegrated  by  the  hot 
water  and  no  hard  lumps  are  left,  cover  the  dish  and  add 
HC1  until  everything  dissolves,  warm  till  effervescence  ceases, 


Notes  on  Metallurgical  Analysis.  13 

wash  off  and  remove  the  cover  and  evaporate  the  solution  to 
dryness  on  a  water  bath  or  otherwise,  when  dry  and  every 
trace  of  odor  of  HC1  has  gone,  add  lOcc  dilute  (1 : 1)  HC1  and 
then  50cc  of  water,  warm  till  the  Na  Cl  has  dissolved,  filter, 
wash  well  with  hot  water,  dry  and  ignite  the  residual  SiO2. 
The  ignition  must  be  repeated  and  the  residue  reweighed 
until  its  weight  does  not  change. 

In  the  filtrate  the  iron,  alumina,  lime  and  magnesia  may 
be  determined  as  in  the  regular  process  and  the  amounts  so 
found  added  to  the  weight  of  the  main  precipitates. 

NOTES  ON  THE  ABOVE   PROCESS. 

1.  Limestones  sometimes  contain  silicates  which  are  decomposed 
by  treatment  with  HC1,  part  of  the  SiO2  going  into  solution  as  hydrate. 
This  is  made  insoluble  by  evaporation  to  dryness.    The  presence  of 
CaCl2  renders  the  dehydration  of  the  SiO2  easy  at  the  temperature  of 
the  water  bath,  a  much  higher  temperature  is  to  be  avoided  as  silica  may 
recombine  with  the  bases  and  so  either  be  redissolved  on  treatment  with 
acid,  or  hold  bases  insoluble. 

2.  When  the  amount  of  residue  is  considerable  it  is  often  necessary 
to  determine  the  silica  it  contains.    In  this  case  it  is  rendered  soluble 
by  fusion  with  excess  of  Na2CO3 — the  addition  of  NaNO3  is  to  be 
avoided  as  it  becomes  caustic  and  attacks  platinum  ware.    The  fused 
mass,    consisting    of    sodium    silicates    and    aluminates,    should   be 
thoroughly  soaked  in  water  till  it  becomes  soft  and  disintegrated,  most 
of  the  sodium  silicate  being  dissolved,  then  on  adding  HC1  a  clear  solu- 
tion without  residue  is  at  once  obtained,  if  the  HC1  is  added  to  the  fused 
mass  before  disintegration  it  causes  a  gelatinous  film  of  SiO2  hydrate 
to  enclose  the  pieces  and  arrests  further  action.      The  clear  dilute 
solution  on  evaporation  to  dryness  deposits  the  silica  in  a  form  more 
easily  washed.    A  single  evaporation  of  the  SiO2  solution  even  if  dried 
for  hours  fails  to  completely  render  the  SiO2  insoluble,  97  to  98%  only 
being  recovered.     The  SiO2  is  not  entirely  pure,  however,  and  these 
errors  tend  to  balance  each  other.    The  impurity  in  the  SiO2  is  largely 
alumina  and  the  dissolved  SiO2  is  largely  precipitated  with  the  alumina 
in  the  subsequent  analysis. 

3.  The  SiO2  is  hard  to  wash,  retaining  alkaline  salts  tenaciously 
it  must  be  thoroughly  washed  with  hot  water  till  the  filtrates  no  longer 
show  a  trace  of  Cl  to  Ag  NO3. 

4.  The  SiO2  must  be  ignited  to  constant  weight,  as  it  retains  water 
most  tenaciously.    A  blast  lamp  is  necessary  to  remove  the  last  traces. 

5.  Fe2O3  and  A12O3  are  absolutely  insoluble  in  solutions  of  NH4C1, 
but  large  excess  of  NH4HO  holds  A12O3  in  solution  to  a  small  extent. 


14  Notes  on  Metallurgical  Analysis. 

This  is  entirely  separated  by  boiling  off  this  excess  of  NH4HO  or  by  the 
presence  of  a  large  excess  of  NH4C1. 

6.  CaH2O2  is  not  completely  soluble  in  NH4HO  unless  sufficient 
NH4C1  be  present,  it  will  be  thrown  down  as  a  white  precipitate,  easily 
mistaken  for  alumina,  so  unless  the  Fe2O3— A12O3  precipitate  is  small  in 
amount  it  is  well  to  redissolve  it  in  HC1  and  reprecipitate  by  NH4HO. 
If  much  Fe  and  Al  are  present  the  precipitate  will  certainly  contain  CaO, 
which  must  be  removed  by  re-solution  and  reprecipitation  after  decanta- 
tion  and  partial  washing.     Solutions  containing  NH4HO  and  CaO  will 
absorb  CO2  on  standing,  hence  the  Fe2O3Al2O3  must  be  filtered  and 
washed  promptly.     On  long  standing  a  crystalline  precipitate  of  CaCO3 
will  sometimes  be  formed  in  the  beaker  with  the  Fe2O3  A12O3 ;  of  course 
in  this  case  re-solution  and  re-precipitation  is  necessary.    Distilled  water 
sometimes  contains  CO 2 which  will  cause  a  precipitation  in  the  same  way. 

7.  Calcium  Oxalate  — Is  very  insoluble,  but  it  is  a  difficult  pre- 
cipitate to  filter  and  wash  if  not  formed  exactly  right.     On  gentle  igni- 
tion below  visible  redness  it  is  changed  to  carbonate,  and  as  such  may 
be  weighed,  slightly  too  high  a  temperature  however  expels  some  CO2. 
The  complete  conversion  to  oxide  requires  a  very  high  temperature  for  a 
long   time.     The  action  of  cone.  H2SO4  on  calcium  oxalate  converts 
it  to  a  CaSO4 — the  action  is  not  violent  and  the  excess  of  H2SO4  pro- 
vided it  is  moderate,  can  be  driven  off  without  danger  of  loss  by  spurt- 
ing.    CaSO4  will  stand  the  cherry  red  heat  of  a  Bunsen  burner  without 
alteration,  the  higher  heat  of  a  blast  lamp  will  cause  it  to  lose  SO3. 

8.  Magnesia  will  precipitate  as  oxalate  in  concentrated  solutions, 
hence  when  much  is  present  a  re-solution  of  the  calcium  oxalate  after  a 
partial  washing  may  be  necessary.      This  is  rarely  the  case,  however, 
if  the  calcium  is  precipitated  in  properly  diluted  solutions.    In  the  anal- 
ysis of  Dolomites  the  calcium  precipitate  must  always  be  redissolved. 

9.  On  concentrating  the  filtrate  from  the  CaC4O4  a  crystalline  pre- 
cipitate1 of  magnesium  oxalate  will  sometimes  separate,  this  can  be 
redissolved  in  HC1  and  added  to  the  solution.    If  it  contains  any  calcium 
oxalate  it  will  leave  a  milky  solution  clearing  slowly. 

10.  As  the  liquid  in  which  the  MgO  is  precipitated  contains  all 
the  added  material  of  the  analysis  careless  addition  of  reagents  may 
give  so  strong  a  solution  of  ammonia  and  soda  salts  that  the  precipita- 
tion of  the  magnesium  phosphate  will  be  incomplete  unless  the  solution 
be  largely  diluted  with  water  and  ammonia,  from  such  a  volume  of 
liquid  the  Mg  will  not  wholly  come  down.    In  such  a  case  the  filtrate 
should  be  evaporated  to  dryness  with  excess  of  HNO3  (3cc  for  each  grm. 
!NH4C1)  to  remove  NH4HO  salts  (which  are  thus  decomposed  into 
nitrogen  and  water)  and  then  any  remaining  magnesia  precipitated. 

See  Cook's  "Select  Methods  Chem.  Analysis." 

11.  There  must  be  enough  ammonium  oxalate  solution  added  to 
convert  all  the  Mg.  as  well  as  Ca  to  oxalates  or  calcium  oxalate  will  not 
completely  precipitate. 


Notes  on  Metallurgical  Analysis.  15 

12.  Sodium  oxalate,  being  very  sparingly  soluble,  will  sometimes 
separate  with  the  Mg  precipitate,  when  the  solution  is  concentrated  and 
much  Na2HPo4  has  been  added ;  in  this  case  the  precipitate,  after  partial 
washing,  must  be  dissolved  in  HC1  and  reprecipitated  by  NH4HO. 

References  — 

SiO2  separation  Jour.  Anal,  and  App.  Chem.  Vol.  IV,  P.  159. 
Mg.  Ca.  separation  Fresenius,  Quant.,  §  73;  §  74;  §  107;  §  104;  §  154. 

DBXBRMINATION    OF    IKOX    IN    ORES. 

Solution. — Most  iron  ores  give  up  practically  all  their  iron  to  hy- 
drochloric acid,  provided  the  acid  be  strong  and  the  ore  sufficiently 
finely  pulverized. 

There  is  danger  of  loss  of  iron  by  volatilization  of  Fe2Cl6  if  a  concen- 
trated solution  of  Fe2Cl4  is  boiled;  hence,  too  great  concentration 
of  the  solution  and  too  hard  boiling  must  be  avoided. 

If  the  residue  from  the  action  of  HC1  is  white  after  ignition,  the 
iron  may  be  considered  all  extracted  unless  the  ore  contains  TiO2,  in 
which  case  an  insoluble  compound  of  iron,  phosphorus  and  titanium 
will  remain,  which  may  not  color  the  residue.  The  presence  of  much 
titanium  causes  a  milky  appearance  in  the  solution  when  diluted,  and 
also  causes  the  insoluble  matter  to  run  through  the  filter  when  washed. 

In  case  of  unknown  ores  it  is  safer  to  fuse  the  insoluble  portion,  as 
in  a  limestone,  and  determine  the  iron  in  this  solution  separately. 

Process. — Pulverize  the  ore  in  an  agate  mortar,  take  a 
very  little  at  a  time  and  rub  it  until  all  trace  of  grit  has 
disappeared  when  tested  between  the  teeth  or  on  the  back  of 
the  hand. 

Weigh  out  one  grm.,  put  it  into  a  dry  No.  0  plain  beaker, 
brushing  off  the  watch  glass  carefully,  add  25  to  30cc  con- 
centrated HC1,  cover  the  beaker  with  a  watch  glass  and  set 
on  a  hot  iron  plate,  digest  at  a  temperature  just  short  of  boil- 
ing until  all  the  iron  is  dissolved,  and  on  shaking  around  the 
beaker  the  residue  appears  light  and  "  flotant"  and  free  from 
dark,  heavy  particles.  This  may  take  from  fifteen  minutes 
to  one  hour  or  more,  according  to  the  ore,  dilute  the  solution 
two  or  three  times  the  volume  and  filter  through  a  5  c.  m. 
filter  into  a  lOOcc  flask.  Wash  the  residue  on  the  filter  till 
it  is  free  from  acid.  By  care  in  letting  the  wash  water  run 
completely  through  each  time,  and  not  more  than  half  filling 
the  filter,  this  can  be  accomplished  with  not  to  exceed  80cc 


16  Notes  on  Metallurgical  Analysis. 

of  filtrate,  dilute  to  the  mark  and  divide  into  two  equal  por- 
tions of  50cc,  then  determine  the  iron  in  each.  The  results 
should  agree  almost  exactly,  and  their  sum  is  the  iron  in  one 
grm.  of  the  ore.  Dry  and  ignite  the  insoluble  portion,  if  it  is 
not  white,  or  if  suspected  of  containing  iron,  fuse  as  in  case 
of  the  insoluble  residue  in  a  limestone.  The  iron  in  the 
HC1  solution  is  then  determined  and  added  to  the  main 
quantity. 

VOLUMETRIC     DETERMINATION     OF     IRON     BY    BICHROMATE 

OF   POTASH,   WITH   REDUCTION   OF    FERRIC 

CHLORIDE  BY  STANNOUS  CHLORIDE. 

The  process  depends  on  the  following  reactions  : 

1.  A  strongly  acid  solution  of  Fe2Cl6,  if  boiling  hot,  is  almost  in- 
stantly reduced  to  FeCl2  by  a  solution  of  SnCl2,  the  end  of  the  reaction 
being  judged  by  the  disappearance  of  the  yellow  color  of  the  iron 
solution. 

SnCl2  -f  Fe2Cl6  =  SnCl4  +  2  FcCl2. 

2.  Any  slight  excess  of  tin  solution  can  be  removed  by  adding 
HgCl2,  which  is  reduced  to  Hg2Cl2,  forming  an  inert,  white  precipitate 
without  action  on  iron  or  bichromate,  the  SnCl2  being  converted  into 
SnCl4, 

SnCl2  -f  2HgCl2  =  SnCl4  +  Hg2Cl2. 

This  reaction  is  satisfactory,  provided  too  much  SnCl2  is  not  present. 
The  HgCl2  is  in  large  excess  and  the  solution  not  too  hot,  otherwise 
metallic  mercury  may  be  formed  as  a  gray  precipitate,  which  will  act 
on  the  bichromate  solution  and  cause  false  results. 

SnCl2  -f  HgCls  =  SnCl4  +  Hg. 

This  reaction  is  at  once  detected  by  the  gray  color  of  the  precipitate 
and  vitiates  the  results. 

3.  When  a  solution  of  bichromate  of  Potash  is  added  to  a  solu- 
tion of  Fed  2  containing  a  considerable  excess  of  HC1  the  FeCl2  is 
instantly  oxidized  to  Fe2Cl6  with  a  corresponding  reduction  of  bichro- 
mate. 

K2  Cr2O7  +  14  HC1+  6FeCl2  =2  KC1  +  Cr2Cl6-f3  Fe2Cl6  +  7  H2O. 
In  the  absence  of  an  excess  of  HC1  a  basis  chromium  salt  may 
separate  as  a  precipitate  and  vitiate  the  results. 

4.  Solutions  containing  FeCl2  strike  an  intense  blue  color  with 
potassium  ferricyanide,  while  solutions  containing  Fe2Cl6  give  a  yellow 
brown  color.    The  ferricyanide  solution  must  be  fresh  as  it  is  reduced 
on  exposure  to  light  or  on  standing  and  it  must  be  dilute  or  its  own 
color  will  interfere. 


Notes  on  Metallurgical  Analysis.  17 

PREPARATION    OF   THE   SOLUTIONS. 

1.  Bichromate  of  Potash  solution.      Heat  a  sufficient 
quantity  of  the  chemically  pure  salt  in  a  platinum  crucible, 
applying  the   heat    carefully   and    avoiding  all  contact   of 
the  flame  with  the  contents  of  the  crucible  (which  would 
cause    reduction),   until  the  material  just  fuses  to  a  dark 
liquid,  withdraw  the  lamp  at  once  and  let  the  crucible  cooL 
During  cooling  the  bichromate  will,  after  solidifying,  grad- 
ually crumble  to  powder. 

Of  this  powder  weigh  out  exactly  8.785  grms.,  dissolve 
it  in  200-300cc  of  cold  water,  transfer  to  a  litre  flask  and 
dilute  to  1  Litre.  Of  this  solution  Ice  should  correspond  to 
exactly  0.01  grms.  of  iron. 

To  test  the  solution,  dissolve  1.4  grm.  of  pure  ammon- 
ium ferrous  sulphate  in  50cc  of  water  containing  5cc  of 
HC1,  run  in  19cc  of  the  bichromate  solution  from  a  burette 
and  then,  after  stirring,  put  a  drop  on  a  white  porcelain 
plate,  add  a  drop  of  the  ferricyanide  solution,  which  will 
strike  a  blue  color  if  the  iron  is  in  excess.  Now  add  the 
bichromate  solution  drop  by  drop,  testing  the  liquid  after 
each  addition  until  instead  of  a  blue  color  it  strikes  an 
orange  yellow.  The  liquid  in  the  burette  should  now  read 
20cc,  if  not  repeat  the  test  and  if  the  two  results  agree, 
make  a  factor  of  correction  which  must  be  applied  to  all 
results.  For  example,  if  instead  of  20cc  20.2  were  taken, 
then  20.2 :  20.=  any  reading :  x  the  true  reading  or  ^  X  any 
reading  =  true  reading  or  percentage  of  iron. 

2.  Stannous   Chloride  Solution.     Dissolve   protochlor- 
ide  of  tin  ("  muriate  of  tin  " )  in  four  times  its  weight  of  a 
mixture  of  three  parts  of  water  to  one  of  HC1 ;  add  scraps 
of  metallic  tin,  and  boil  till  the  solution  is  clear  and  color- 
less.    ( Keep  the  solution  in  a  closed  dropping  bottle  con- 
taining metallic  tin.) 

3.  A   saturated   solution  of  Mercuric  Chloride.     Keep 
an  excess  of  the  salt  in  a  bottle  and  fill  up  with  water  from 
time  to  time. 


18  Notes  on  Metallurgical  Analysis. 

4.  A  one  per  cent,  solution  of  Ferricyanide  of  Potas- 
sium. This  must  be  made  fresh  when  wanted. 

The  other  solutions  keep  indefinitely.  The  Sn  C12  solu- 
tion must,  however,  be  kept  from  the  air. 

PROCESS   FOR  THE  ASSAY. 

Transfer  one-half  the  iron  solution  to  a  porcelain  dish, 
add  5cc  HC1,  heat  to  boiling,  and  drop  in  the  tin  solution 
slowly  till  the  last  drop  makes  the  solution  colorless.  Re- 
move the  lamp  and  cool  the  liquid  by  setting  the  dish  in 
cold  water.  When  nearly  cold  add  at  once  15cc  of  the 
mercuric  chloride  solution,  stirring  the  solution  with  a  glass 
rod.  Let  it  stand  three  or  four  minutes.  A  slight  white 
precipitate  should  form  ;  none  at  all,  or  a  heavy  grayish  one 
renders  the  results  doubtful. 

Now  run  in  the  bicromate  solution  until  a  drop  of  the 
liquid  tested  on  the  porcelain  plate  with  a  drop  of  ferri- 
cyanide  solution  no  longer  shows  a  blue,  but  a  yellow  color. 

The  number  of  cc  used  multiplied  by  2  gives  the  per- 
centage of  iron  in  the  sample. 

Repeat  the  process  on  the  second  half  of  the  iron  solu- 
tion running  in  at  once  nearly  the  full  amount  of  bichromate 
and  then  finishing  drop  by  drop.  If  the  two  results  nearly 
agree,  average  them. 

This  analysis  can  be  completed  in  an  hour. 

In  the  case  of  mill  cinder  and  other  decomposable  slags,  add  to  the 
finely  powdered  slag  20cc  water  and  stir  up  well  to  prevent  the  cinder 
"caking"  on  the  bottom  of  the  beaker,  then  add  20-30cc  HC1  and  pro- 
ceed as  before. 

In  the  case  of  materials  not  attacked  by  HC1,  fusion  with  Na2CO3 
must  be  resorted  to  to  get  the  iron  in  a  soluble  form. 

Titanium,  when  present,  will  not  affect  this  process  provided  care 
be  taken  to  fuse  the  residue  and  add  its  solution  to  the  main  filtrate. 
When  zinc  is  used  to  reduce  the  solution  the  TiO2  will  vitiate  the  results. 

Titration  with  permanganate  of  potash  after  reduction  by  metallic 
zinc,  is  used  by  many  chemists ;  for  description  of  this  process  see  Blair's 
Chem.  An.  Iron,  p.  200 ;  also  for  Clemens  Jones's  apparatus  for  reduc- 
ing iron  solutions  by  filtration  through  powdered  zinc,  see  Trans.  Inst. 
Min.  Engs.,  Vol.  XVII,  p.  411. 


Notes  on  Metallurgical  Analysis.  19 

SILICIOUS   MATTER  AND   SILICA   IN   IRON   ORES. 

Treat  one  grm.  of  the  finely  pulverized  ore  in  a  caserole 
or  4  in.  porcelain  dish  with  25cc  cone.  HC1  evaporate  the  solu- 
tion to  dryness  and  heat  on  an  iron  plate  until  the  residue  is 
dry  and  scaly,  dissolve  in  lOcc  cone.  HC1  by  warming,  dilute, 
filter  on  a  small  filter,  wash  dry,  ignite  and  weigh  as 
"silicious  matter."  This  consists  of  free  silica,  silicates,  prin- 
cipally of  alumina,  sometimes  titanium  oxide  and  iron  sul- 
phide and  occasionally  barium  sulphate. 

Mix  the  ignited  u insoluble  silicious  matter"  with  6-8 
times  its  weight  of  dry  Na2CO3 ;  fuse  in  a  platinum  crucible 
and  extract  with  water,  acidify  with  HC1,  evaporate  to  dry- 
ness  and  heat  on  a  water  bath  until  all  smell  of  HC1  has  gone. 
Add  water  and  HC1  and  evaporate  again  to  dryness ;  again 
take  up  with  HC1,  add  water,  filter  and  wash  with  hot  water, 
dry,  ignite  and  weigh  the  SiO2.  The  second  evaporation  is 
not  necessary  unless  very  exact  results  are  required,  and  in 
this  case  it  is  necessary  to  determine  the  impurity  in  the 
SiO2  by  hydrofluoric  acid,  as  follows : 

To  the  weighed  SiO2  in  the  platinum  crucible  add  1-10 
drops  cone.  H2SO4  (enough  to  moisten  it) ;  then  add  cone, 
pure  HF1  until  the  SiO2is  completely  dissolved.  Evaporate 
this  to  dryness  under  a  good  hood,  dry  and  ignite  the  residue, 
deduct  the  weight  of  this  from  the  weight  of  the  SiO2  first 
fdund  and  the  difference  is  pure  SiO2. 

The  silica  in  the  above  process  is  completely  volatilized  as  gaseous 
silicon  fluorid,  while  alumina,  iron  oxide,  titanic  oxide  and  barium  sul- 
phate remain  unaltered. 

Should  the  silica  contain  alkaline  chlorides  due  to  imperfect  wash- 
ing, these  will  be  converted  to  sulphates,  and  so  the  residue  will  be  too 
heavy.  This  error  need  only  be  feared  if  there  is  considerable  residue. 


20  Notes  on  Metallurgical  Analysis. 


OK    PHOSPHORUS     IN    IRON, 
STKBL,  AND  IROX  ORBS. 

The  following  methods  are  in  general  use  and  depend  upon  the 
separation  of  the  phosphorus  from  the  various  bases,  as  phosphododeca 
molybdate  of  ammonia. 

This  substance,  the  so-called  "yellow  precipitate,"  when  dried  at 
130.Cy  has  uniformly  the  composition  12  MoO3PO4  (NHJ3.  This  form- 
ula requires  1.65  per  cent,  of  phosphorus.  The  average  of  many  most 
carefully  conducted  experiments  has  shown  that  the  precipitate 
contains  1.63  per  cent,  phosphorus  within  very  narrow  limits  if  free 
from  admixed  molybdic  acid  or  other  impurities. 

The  precipitate  is  only  obtained  pure  when  formed  under  very  exact 
conditions,  and  is  easily  affected  by  subsequent  treatment,  so  that  all 
methods  depending  upon  the  weighing  of  the  u  yellow  precipitate  "  or 
its  volumetric  determination  must  be  carried  out  rigorously  according 
to  the  prescribed  directions  in  every  detail. 

When  a  solution  of  molybdate  of  ammonia  in  nitric  acid  is  added 
to  an  acid  solution  containing  phosphoric  acid.  The  whole  of  the  phos- 
phoric acid  is  precipitated  as  the  yellow  "phospho  molybdate  of  am- 
monia," under  the  following  conditions  : 

1.  All  the  phosphorus  must  be  present   as  tribasic   ("ortho") 
phosphoric  acid. 

2.  A  decided  excess  of  ammonium  nitrate  or  sulphate  must  be 
present. 

The  precipitation  is  most  rapid  when  the  solution  contains  between 
five  and  ten  per  cent,  of  the  salt. 

3.  A   certain   excess  of   free   acid  must  be  present  —  preferably 
nitric,  but  not  necessarily  so.    This  must  amount  to  at  least  25  mole- 
cules of  acid  for  each  molecule  of  P2O5  present,  and  must  be  increased 
when  sulphates  are  present. 

4.  Too  great  an  excess  of  free  acid  must  not  be  present,  as  this 
causes  decomposition  and  partial  re-solution  of  the  precipitate.    This 
action  becomes  perceptible  when  over  80  molecules  of  acid  are  present  to 
each  molecule  of  P2O5. 

This  action  of  free  acid  is  prevented  by  an  excess  of  molybdic  acid* 
This  excess  must  be  greater  as  the  amount  of  free  acids  is  greater. 

5.  The  yellow  precipitate  is  insoluble  in  the  solution  of  molyb- 
date of  ammonia  in  nitric  acid  ;  in  solutions  of  ammonium  salts,  if  neu- 
tral or  only  very  slightly  acids,  but  if  strongly  acid  they  attack  the  pre- 
cipitate, which  is,  however,  reprecipitated  by  the  addition  of  molybdic 
acid  solution  to  the  liquid.     It  is  also  practically  insoluble  in  a  solution 
of  potassium  nitrate  when  neutral  and  not  too  dilute  (containing  at 
least  2  per  cent.).  Solutions  of  salts  of  organic  acids  usually  dissolve  the 
precipitate  to  some  extent.    From  these  solutions  nitric  acid  and  am- 


Notes  on  Metallurgical  Analysis.  21 

moiiium  nitrate,  in  some  cases,  reprecipitate  the  material  in  others,  e.  g., 
tartaric  acid,  oxalic  acid  —  probably  not  completely. 

The  mineral  acids,  HC1,  HNO3,  H2SO4,  all  have  a  solvent  action 
on  the  precipitate  even  in  the  presence  of  ammonium  nitrate.  HNO3 
has  the  least,  H2SO4  the  most. 

Pure  water  decomposes  the  precipitate  to  a  slight  extent  and  be- 
comes milky,  causing  the  material  to  run  through  the  filter. 

6.  Precipitation  is  much  more  rapid  from  hot  than  from  cold 
solutions,  but  in  time  it  is  probably  complete  at  any  temperature.    The 
precipitate  from  hot  solution  is  more  crystalline  and  dense ;  from  cold, 
more  granular  and  fine,  and  harder  to  filter  and  wash. 

7.  Agitation  greatly   accelerates  precipitation  in  this  as  well  as 
in  all  other  chemical  reactions. 

8.  The  precipitate  dried  at  ordinary  temperatures  to  constant 
weight  retains  a  little  acid  and  water,  which  it  looses  when  dried  at 
130°C.    By  washing  the  precipitate  with  a  neutral  solution  of  ammonium 
or  potassium  nitrate  it  can  be  freed  from  all  this  acid  without  drying. 

9.  SiO2  in  solution  does  not  seem  to  interfere  with  the  complete 
precipitation  of  phosphorus  if  other  conditions  are  right,  but  a  small 
trace  of  the  SiO2  usually  comes  down  with  the  precipitate,  especially 
if  the  solution  is  too  concentrated,  or  too  warm,  and  stands  too  long. 
If  the  solution  is  rather  dilute,  not  too  hot,  and  is  filtered  promptly, 
the  yellow  precipitate  can  be  obtained  in   solutions  containing  con- 
siderable SiO2  practically  free  from  it. 

10.  "  Organic  matter  "  has  usually  been  supposed  to  interfere  with 
the  precipitation  of  phosphorus,  but  it  is  probable  that  in  many  cases, 
noticeably  in  steel  analysis,  the  bad  results  attributed  to  this  cause  were 
due  to  the  fact  that  the  phosphorus  was  not  all  oxidized  to  the  tribasic 
form. 

11.  When  arsenic  acid  is  present  in  the  solution  with  phosphorus, 
it  will  be  precipitated  at  the  same  time  in  amounts  increasing  with  the 
temperature.    Only  very  small  traces  come  down  at  temperatures  not 
exceeding  25°C. 

12.  Molybdic  acid  may  separate  with  the  precipitate  as  a  light 
crystalline  deposit.    This  free  MoO3  is  only  soluble  with  difficultly  in  acids 
and  cannot  be  washed  out  of  the  yellow  precipitate.     Its  separation 
must  always  be  guarded  against  when  the  yellow  precipitate  is  to  be 
weighed  or  titrated.    It  forms  when  the  amount  of  molybdic  acid 
present  is  too  great,  the  solution  too   concentrated,  or  too  dilute,  too 
strongly  acid  or  too  nearly  neutral.     Too  high  a  temperature  precipi- 
tates it.    The  addition  of  strong  HNO8  to  a  solution  of  molybdic  acid 
will  sometimes  produce  it,  or  adding  molybdic  acid  solution  to  concen- 
trated nitric  acid  solutions  of  iron. 

13.  When  the  yellow  precipitate  is  thrown  down  in  a  solution  con- 


22  Notes  on  Metallurgical  Analysis. 

taining  much  iron  and  not  sufficient  acid,  basic  iron  salts  are  liable  to 
accompany  it,  making  it  reddish  in  color. 

14.  The  yellow  precipitate,  if  pure,  is  easily  and  completely 
soluble  in  NH4HO,  if  it  contains  iron  the  solution  will  be  turbid— from 
this  solution  the  phosphoric  acid  is  completely  precipitated  by  u  mag- 
nesia mixture  "  as  MgNH4PO4.  If  the  yellow  precipitate  contains  any 
SiO2  this  will  also,  in  part  at  least,  dissolve  in  the  NH4HO  and  separate 
with  the  magnesia  precipitate,  making  it  a  little  flocculent.  By  cautiously 
adding  HC1  to  the  NH4HO  solution  until  nearly  neutral  before  adding 
the  Mg  mixture,  and  letting  it  stand  for  some  time  in  a  warm  place  the 
SiO2  separates  completely  and  may  be  filtered  off,  then  the  phosphorus 
precipitated  in  the  filtrate.  In  precipitating  with  magnesia  mixture, 
add  the  reagent  drop  by  drop  and  stir  the  liquid  constantly,  so  that  the 
precipitate  separates  slowly  and  in  a  crystalline  form,  otherwise  it  will 
be  impure,  containing  magnesia  in  excess  and  molybdic  acid.  The 
Mg2P2O7  must  be  ignited  thoroughly  with  access  of  air  to  drive  off  any 
trace  of  MoO3  it  may  retain. 

For  properties  of  "  yellow  precipitate "  and  effects  of  impurities  and  associated  sub- 
stances, see 

Hundeshagen,  Zeitschrift  An.  Chem.,   vol.  XXVIII,  p.  141;  also   Chem.  News,  vol. 

LX,  p,  169. 

Drown — Trans.  Inst.  Min.  Engrs.,  vol.  XVIII,  p.  90. 
Shimer  —  Trans.  Inst.  Min.  Engrs.,  vol.  XVII,  p.  100. 
Hamilton — Jour.  Soc.  Chem.  Industry,  vol.  X,  p.  904;  also  Jour.  Anal,  and  App. 

Chem.  vol.  VI,  p.  572. 

Babbitt  —  Jour.  An.  and  App.  Chem.,  vol.  VI,  p.  381. 
Precipitation  by  magnesia  — 

Gooch  —  Am.  Chem.  Jour.,  vol.  I,  p.  391, 

GRAVIMETRIC  METHOD   FOR   PHOSPHORUS  WITH  FINAL  PRE- 
CIPITATION  AS   MAGNESIUM    PHOSPHATE. 

This  is  free  from  the  chances  of  error  due  to  the  accidental  impur- 
ity of  the  yellow  precipitate.  It  is  gravimetric  throughout,  and  the 
phosphoric  acid  is  finally  weighed  in  a  form  not  subject  to  variation  in 
composition.  It  is  independent  of  the  kind  of  material  treated  and  the 
per  cent,  of  phosphoric  acid ;  hence,  is  a  standard  method  to  which  final 
reference  must  be  made  in  all  important  determinations. 

Process  for  Iron  Ores. — In  the  absence  of  more  than 
traces  of  titanium  and  arsenic.  Weigh  1  to  5  grms.,  according 
to  the  percentage  of  phosphorus,  of  the  very  finely  pulverized 
ore,  put  into  a  4-inch  porcelain  dish  or  caserole,  add  Ice 
HNO3,  then  cone.  HC1,  using  15cc,+10cc  more  for  each  grm. 
of  ore  taken  (/.  for  three  grms.  45cc),  cover  with  a  watch 
glass  and  warm  till  all  the  iron  appears  to  be  in  solution,  boil 


Notes  on  Metallurgical  Analysis.  23 

down  to  dryness,  keeping  covered  to  avoid  spattering,  dry  on 
a  hot  plate  till  the  acid  is  expelled,  add  30cc  cone.  HC1,  cover 
and  digest  till  all  the  iron  is  dissolved.  Now  boil  down  until 
the  liquid  does  not  exceed  10  or  15cc.  If  the  dish  is  kept 
covered  there  need  be  no  formation  of  dry  salt  on  the  sides. 
Add  water  till  the  volume  is  40  or  50cc,  washing  off  the  cover 
and  the  sides  of  the  dish,  filter  through  a  small  filter  into  a 
No.  1  or  2  beaker,  transfer  the  residue  to  the  filter  and  wash 
until  there  is  no  acid  taste  to  the  washings. 

Dry  and  ignite  the  residue ;  for  ordinary  ores  it  is  prac- 
tically free  from  phosphorus,  and  may  be  thrown  away  if 
light  colored  and  not  too  large  in  amount.  In  special  or 
doubtful  cases,  however,  fuse  it,  like  the  insoluble  residue 
from  a  limestone,  and  after  filtering  out  the  silica,  add  am- 
monia to  the  filtrate,  heat  to  boiling  and  let  the  precipitate 
settle,  decant  off  the  clear  liquid,  dissolve  the  precipitate  in 
a  few  cc  of  HNO3,  add  20cc  of  molybdic  acid  solution  and 
warm.  Should  a  u  yellow  precipitate  "  separate,  it  must  be 
added  to  that  obtained  in  the  main  solution. 

The  filtrate  and  washings  from  the  insoluble  matter  of 
the  ore  should  not  exceed  150cc.  To  this  add  lOcc  of  cone. 
HNO3,  then  NH4HO,  until  a  precipitate  is  formed  which  does 
not  disappear  on  stirring,  then  3cc  of  cone.  HNO3  which 
must  redissolve  the  precipitate  and  give  a  clear  amber-col- 
ored liquid,  not  at  all  red  in  tint.  The  solution  will  now  be 
quite  warm.  Add  at  once  from  a  pipette  in  a  fine  stream 
50cc  of  "  molybdic  acid  solution,"1  stirring  the  liquid  vigor- 
orously  all  the  time,  and  continue  this  stirring  for  about  three 
minutes.  Let  the  solution  stand  in  a  warm  place  until  it  is 
clear  and  the  precipitate  has  all  settled  ( which  should  not 

1.  Preparation  of  the  Molybdic  Acid  Solution. — Add  to  100  grms.  of  molybdic  acid,  300cc 
of  water,  and  then  120cc  of  strong  (26°)  NHiHO.  This  will  dissolve  the  MoO3,  and  the  solu- 
tion must  smell  distinctly  of  ammonia.  If  it  does  not,  add  more  NH^HO.  Unless  the  solution  is 
clear,  filter  it,  then  dilute  to  about  SOOcc.  Now  mix  500cc  of  cone.  HNOs  with  enough  water  to 
make  about  1200cc.  Cool  both  solutions  and  mix  \>y  pouring  the  solution  of  molybdic  acid  into 
the  diluted  HNO§.  The  volume  should  now  be  2000cc.  Let  the  mixture  stand  a  day  or  two,  or 
until  any  small  precipitate  settles  and  use  the  clear  liquid.  If  the  solution  of  molybdic  acid  in 
NH.4.HO  is  not  diluted  sufficiently,  or  if  the  above  directions  are  not  followed  as  to  mixing,  the 
molybdic  acid  may  separate  from  the  solution.  40cc  of  this  solution  will  precipitate  about  0.04 
grms.  of  phosphorus. 


24  Notes  on  Metallurgical  Analysis. 

require  to  exceed  one  hour),  remove  a  portion  of  the  clear 
liquid  with  a  pipette  and  test  it  by  adding  a  little  more  molyb- 
dic  acid  solution  and  warming  to  see  if  all  the  P2O5  is  down. 

Filter  the  liquid  through  a  7  c.  m.  filter,  transfer  the 
precipitate  to  the  filter  and  wash  until  free  from  iron,  with  a 
5  per  cent,  solution  of  ammonium  nitrate  very  slightly  acid- 
ified with  HNO3.  The  washing  must  be  thorough  or  diffi- 
culty will  be  experienced  in  redissolving  the  precipitate,  as 
in  this  case  phosphate  of  iron  and  alumina  may  form  and 
cause  the  filter  to  clog  up.  When  the  precipitate  is  washed 
put  the  beaker  in  which  the  precipitation  was  made  under 
the  funnel  and  redissolve  the  precipitate  on  the  filter  with 
dilute  NH4HO.  When  dissolved  and  the  liquid  run  through 
wash  the  filter  with  water  three  or  four  times,  then  with  a 
little  dilute  HC1,  and  then  again  with  water.  The  filtrate 
should  now  be  clear  and  colorless.  If  it  is  cloudy  or  colored 
(by  a  little  iron),  add  HC1  until  the  liquid  is  acid  ( the  yellow 
precipitate  usually  separates),  then  add  four  or  five  drops  of  a 
saturated  solution  of  citric  acid,  then  NH4HO  to  make  the 
liquid  strongly  alkaline.  This  will  give  a  clear  liquid,  the 
^ citric  acid  holding  the  iron  in  solution. 

Now  add  drop  by  drop  a  considerable  excess  of  "  mag- 
nesia mixture,"1  stirring  the  liquid  constantly.  This  excess 
must  be  estimated  from  the  probable  amount  of  phosphor- 
us in  the  ore  taken.  Continue  to  stir  the  solution  vigor- 
ously for  four  or  five  minutes,  then  add  NH4HO  until  the 
solution  smells  strongly  of  ammonia. 

Let  it  stand  until  the  precipitate  of  Mg  NH4PO4  has  set- 
tled completely  ( one  or  two  hours).  The  precipitate  should 
be  white  and  crystalline ;  if  red  or  flaky,  the  results  will  be 
inaccurate. 

Filter  on  a  small  filter  or  better  on  a  Gooch  perforated 

1.  Preparation  of  "Magnesia  Mixture." — Dissolve  22  grms.  of  dry  calcined  magnesia  in 
just  sufficient  dilute  HC1.  When  dissolved  add  more  of  the  magnesia  until  some  remains  un- 
dissolved,  now  boil ;  all  iron  oxide,  alumnia  and  phosphoric  acid  will  be  precipitated.  Filter  the 
solution,  add  280  grms.  of  NH4C1,  SOOcc  water  and  200cc  cone.  NH4HO  (26°).  When  all  dis- 
solves, dilute  to  2000cc.  Let  stand  a  day  or  two  and  decant  or  filter  the  solution  from  any  precip- 
itate. lOcc  of  this  will  precipitate  about  0.07  grms.  of  phosphorus. 


UNIVERSITY 
Notes  on  Metallurgical  Anal^^Of  r        :QrtXK  ^^25 


crucible.  Wash  with  water  containing  ^  its  volume  of  cone. 
NH4HO  and  a  little  NH4NO3,  dry,  ignite  and  weigh  as 
Mg2P2O7,  containing  0.279  of  phosphorus. 

It  is  essential  that  the  filtrate  from  the  magnesia  precip- 
itate should  give  at  once  a  strong  test  for  Mg  ( when  tested 
with  a  drop  of  a  solution  of  sodium  phosphate),  as  a  consid- 
erable excess  of  magnesia  is  essential  to  completely  precipi- 
tate the  phosphorus. 

When  ores  contain  titanium  in  any  amount  the  solution  on  dilution 
before  filtration  may  become  turbid  and  the  residue  run  through  the 
filter  on  washing.  In  this  case  the  residue  will  retain  iron  and 
phosphorus. 

Modification  of  the  Process  on  Account  of  Titanium. — First 
clear  the  filtrate  from  the  insoluble  matter  by  warming  with 
the  addition  of  nitric  acid,  and  before  adding  ammonia,  if  it 
does  not  become  quite  clear,  no  matter,  proceed  with  it 
exactly  as  before.  After  the  filter  paper  containing  the  yel- 
low precipitate  has  been  washed  out  with  NH4  HO  and  HC1 
it  must  not  be  thrown  away,  as  it  may  retain  phosphorus 
and  titanic  acid,  burn  it  and  add  what  is  left  to  the  insoluble 
residue.  Now  mix  the  insoluble  residue  and  the  burned 
filter  above  mentioned  with  eight  times  its  weight  of  dry 
Na2  CO3  and  fuse  as  for  silica.  Boil  the  fusion  with  water 
until  thoroughly  disintegrated.  The  phosphorus  passes 
into  solution  as  phosphate,  while  the  TiO2  remains  insoluble 
as  titanate.  Filter  the  liquid  from  the  insoluble  matter,  acid- 
ulate the  filtrate  with  HNO3,  evaporate  it  to  dryness,  add  a 
little  HNO3,  then  water  and  filter  from  the  separated  SiO2. 

Add  to  the  filtrate  25cc  molybdic  acid  solution  arid  warm, 
filter  off  the  yellow  precipitate  and  treat  it  exactly  like  that 
from  the  main  solution.  Add  the  phosphorus  thus  obtained 
to  that  obtained  from  the  first  solution. 

See  a  valuable  paper  by  Drown  and  Shiiner,  Trans.  Inst.  Min. 
Engrs.,  voL  X.,  p.  137. 

When  ores  contain  arsenic  there  is  always  danger  that 
the  final  results  will  be  high  from  the  presence  of  magnesium 
arsenate. 


26  Notes  on  Metallurgical  Analysis. 

In  this  case  proceed  as  follows :  To  the  filtrate  from  the  insoluble 
residue,  which  should  be  in  a  small  Erlenmeyer  flask,  add  a  solution  of 
Na2CO3  until  the  liquid  becomes  dark  colored,  then  add  small  portions 
of  pure  crystallized  sodium  sulphite  ( Na2SO3 ),  which  must  be  free  from 
phosphorus.  (This  is  best  done  by  dissolving  the  salt  in  water  1  to  5,  add 
HC1  until  the  solution  reacts  slightly  acid  and  use  this  solution).  Warm 
the  solution,  shaking  occasionally  until  up  to  boiling.  If  any  precipi- 
tate forms  redissolve  it  by  a  few  drops  of  HC1.  By  this  time  the  solu- 
tion should  be  colorless  and  all  the  iron  reduced  to  the  ferrous  form ;  if 
not,  continue  the  warming.  Finally  add  lOcc  HC1,  and  boil  until  all  the 
odor  of  SO2  has  gone  ( usually  about  three  minutes ).  Remove  from  the 
lamp  and  pass  a  stream  of  H2S  gas  through  the  liquid  for  fifteen  or 
twenty  minutes,  or  till  all  the  As2S3  is  precipitated.  (The  volume  of 
the  liquid  should  not  exceed  150cc.)  The  As  and  any  Cu  pres- 
ent separate  completely  as  sulphides.  Filter  the  solution  rapidly  into 
a  beaker  and  wash  with  a  little  H2S  water.  Now  boil  the  filtrate  till 
all  the  odor  of  H2S  has  disappeared,  then  add  HNO3  drop  by  drop  to 
the  hot  liquid  until  the  change  of  color  shows  all  iron  to  be  changed  to 
the  ferric  form,  and  the  liquid  becomes  perfectly  clear.  A  faint  cloud  of 
separated  sulphur  may  form,  but  will  disappear  on  heating  and  does  no 
harm.  From  this  point  proceed  exactly  as  with  the  filtrate  from  the  in- 
soluble residue  in  ores  when  As  was  not  present. 

The  process  depends  upon  the  complete  precipitation  of  arsenic  by 
H2S  in  hot  strongly  acid  solutions.  The  reduction  of  the  iron  is  neces- 
sary to  prevent  a  large  separation  of  sulphur  from  the  action  of  the 
H2S  on  the  Fe2Cl6. 

The  As2S3  precipitate  may  be  used  for  the  determination  of  arsenic, 
provided  the  solution  has  not  been  boiled  too  long  before  precipitation 
by  H2S,  which  will  cause  volatilization  of  As2Cl6.  See  Fresenius* 
Quant.  Anal.,  for  details. 

DETERMINATION  OF  PHOSPHORUS  IN    BLACK    BAND  ORES  AND  OTHERS 
WHICH  CONTAIN  MUCH  CARBONACEOUS  MATTER. 

These  should  be  weighed  out  in  a  porcelain  crucible  and  carefully 
burned,  taking  care  not  to  heat  so  rapidly  as  to  cause  loss  by  blowing 
out  of  fine  particles.  After  all  "flaming"  has  ceased,  turn  the  crucible 
on  its  side  and  heat  with  access  of  air  till  the  carbon  is  gone  and  an 
"ash"  is  left.  Treat  this  by  the  regular  process.  Avoid  a  high  temper- 
ature in  burning  or  the  material  will  cake,  thus  causing  imperfect  solu- 
tion. A  dull  red  heat  is  sufficient. 

DETERMINATION  OF  PHOSPHORUS  IN  MILL  CINDER. 

Two  points  here  need  attention.  First^  the  material  being  a  solu- 
ble silicate,  it  should  be  decomposed  by  weak  acid  and  evaporated  to 
dryness,  as  in  the  case  of  the  determination  of  silica  after  fusion. 


Notes  on  Metallurgical  Analysis.  27 

Second,  all  mill  cinder  contains  particles  of  metallic  iron  which  contain 
phosphorus  as  phosphide,  and  would  give  off  PH3  gas  when  dissolved 
in  HC1,  so  HNO3  must  be  used  to  oxidize  the  phosphorus.  Proceed  as 
follows:  Weigh  1  grm.  into  a  porcelain  dish,  add  20cc  HNO3 1.2  sp. gr.» 
stir  well  to  prevent  caking  and  warm  till  action  ceases,  then  add  lOcc 
H2O  and  lOcc  cone.  HOI.  Evaporate  to  dry  ness  and  heat  on  an  iron 
plate  to  200°C  for  half  an  hour.  Add  lOcc  HC1,  digest  till  all  dissolves. 
Dilute,  filter,  and  proceed  as  with  an  ore. 

DETERMINATION  OF  PHOSPHORUS  IN  IRON  AND  STEEL  BY  THE 
MOLYBDATE-MAGNESIA  PROCESS. 

The  phosphorus  in  iron  and  steel  exists  principally  as  phosphide. 
When  these  metals  are  treated  with  ordinary  solvents,  the  oxidation  of 
the  phosphorus  is  incomplete  ;  when  treated  with  non-oxidizing  acids 
( HC1  H2SO4),  part  of  the  phosphorus  passes  off  as  gaseous  H3P.  Even 
concentrated  HNO3  probably  fails  to  convert  all  the  phosphorus  into 
tribasic  phosphoric  acid. 

These  metals  also  contain  carbon  compounds  which  pass  into  solu- 
tion in  HNO3  as  a  dark  colored  substance,  and  the  presence  of  this  dis- 
solved carbonaceous  matter  is  generally  supposed  to  interfere  with  the 
precipitation  of  the  yellow  precipitate,  though  it  seems  probable  from 
recent  experiments  that,  if  the  phosphoric  acid  were  in  the  tribasic 
state,  this  organic  matter  would  be  without  influence.  It  is  certain, 
however,  that  unless  the  oxidizing  action  is  strong  enough  to  destroy 
completely  this  carbonaceous  matter,  the  phosphorus  will  not  be  all 
oxidized  and  can  not  be  all  precipitated. 

The  most  generally  used  and  oldest  method  of  oxidation  is  the 
"dry  method."  It  consists  in  dissolving  the  metal  in  HNO3  concen- 
trated, or,  more  generally,  dilute  (1.2  sp.  gr.)  evaporating  the  solution  to 
dryness.  The  dry  mass  of  basic  ferric  nitrate  is  then  heated  to  about 
200°C  for  some  time.  At  this  temperature  the  salts  are  decomposed,  the 
iron  converted  largely  to  ferric  oxide,  and  the  dissolved  carbon  and 
phosphorus  completely  oxidized.  This  residue  can  then  be  dissolved  in 
HC1  and  treated  like  an  ore.  The  method  is  certain  and  independent  of 
delicate  reaction. 

Several  "wet"  methods  of  oxidation  have  been  proposed  and  used 
with  apparent  success.  Among  these  are  oxidation  in  nitric  acid  solu- 
tion by  chromic  acid,  and  by  permanganate  of  potash.  Aqua  regia  fails 
to  cause  complete  oxidation,  as  probably  does  KC1O3  and  HC1.  When 
permanganate  is  used  there  is  a  separation  of  MnO2  which  holds  phos- 
phorus insoluble  and  must  be  all  dissolved  by  adding  a  reducing  agent, 
such  as  oxalic  acid  or  ferrous  sulphate.  Wet  methods  are  quicker,  but 
must  be  restricted  to  the  class  of  material  to  which  their  adaptability 
has  been  proved. 


28  Notes  on  Metallurgical  Analysis. 

Process  for  Phosphorus  in  Iron  and  Steel. — Take  from 
1  to  5  grms.  of  the  well  mixed  borings.  Treat  them  in 
a  covered  caserole  or  dish  with  25  to  75cc  of  HNO3  1.2 
sp.  gr.  (made  by  mixing  water  and  cone.  HNO3  in  equal 
parts).  Add  the  acid  cautiously  to  prevent  boiling  over, 
heat  till  action  has  ceased,  boil  down  to  dryness,  using 
care  to  prevent  spattering,  and  keeping  the  dish  covered. 
When  dry,  set  on  a  hot  iron  plate  and  heat  the  dish  to  about 
200°C  for  from  30  minutes  to  1  hour,  at  the  end  of  this  time 
the  material  should  be  hard  and  scaly  and  show  no  trace  of 
acid  fumes.  Now  add  from  15  to  25cc  cone.  HC1,  digest  till 
all  the  iron  is  dissolved  and  proceed  as  in  iron  oies.  Many 
steels  will  leave  no  residue  insoluble  in  HC1.  In  this  case 
filtration  is  unnecessary. 

The  phosphorus  retained  in  the  residue  in  case  of  irons 
and  steels  practically  amounts  to  nothing. 

To  make  the  filtration  easy,  add  to  the  above  HC1  solution  about 
50cc  H2O,  boil  this  solution  5  minutes  and  then  let  settle  completely, 
decant  off  the  clear  liquid,  transfer  and  wash  the  residue  with  warm 
water  adding  a  little  HC1  at  first,  this  treatment  seems  to  cause  a  con- 


DETERMINATION   OF    THE   PHOSPHORUS   BY  WEIGHING  THE 
YELLOW    PRECIPITATE. 

This  method  is  very  generally  used  as  a  "  rapid  method." 

That  the  yellow  precipitate  obtained  may  be  of  constant  composi- 
tion, the  details  of  the  process  must  be  carried  out  exactly  as  given. 

As  the  yellow  precipitate  contains  1.63%  of  phosphorus  it  is  con- 
venient to  take  that  quantity  of  the  material  in  grammes  —  as  in  that 
case  the  weight  of  the  precipitate  in  grammes  will  be  the  per  cent,  of 
phosphorus. 

The  drying  and  weighing  of  over  0.4  grm.  of  yellow  precipitate  is 
difficult,  hence  for  ores  having  over  T%%  of  phosphorus  take  \  the 
above  amount  (0.815  grms.). 

The  following  details  are  essentially  those  given  by  E.  F.  Wood  in 
an  important  paper  in  The  Zeitschrift  fur  Anal.  Chem.,  vol.  25,  p.  489: 

Process  for  Iron  Ores. — Weigh  1.63  grms.  of  the  finely 
pulverized  ore  into  a  4-inch  dish  or  caserole,  add  25cc  cone. 
HC1,  digest  and  evaporate  dry,  heat  as  in  the  first  process. 


Notes  on  Metallurgical  Analysis.  29 

Now  add  20cc  HC1,  digest  till  all  the  iron  is  dissolved,  add 
30cc  H2O,  boil,  settle  and  filter  into  a  No.  1  beaker,  wash 
with  small  portions  of  water,  letting  each  run  through  before 
adding  the  next,  the  volume  of  filtrate  and  washings  need  not 
exceed  70  or  80cc.  Now  add  35cc  concentrated  HNO3,  boil 
down  rapidly  until  the  volume  of  the  liquid  is  15cc  (judged 
by  putting  this  amount  of  water  in  a  similar  beaker  and 
comparing  the  two),  take  off  the  hot  plate,  wash  off  the  cover 
and  add  water,  so  that  in  all  from  15  to  20cc  of  water  are 
added,  that  is,  at  least  as  much  water  as  solution,  stir  the  solu- 
tion and  add  from  a  pipette  40cc  of  molybdic  acid  solution 
which  should  be  at  a  temperature  of  not  less  than  25°C  so 
that  the  mixed  solution  shall  be  at  a  temperature  of  not  less 
than  40°C.  Stir  vigorously  for  2  or  3  minutes,  set  in  a  warm 
place  (not  on  a  hot  plate  or  water  bath,  which  may  cause 
precipitation  of  molybdic  acid )  until  the  precipitate  has  set- 
tled and  the  liquid  is  perfectly  clear  —  this  will  take  30  min- 
utes to  an  hour  according  to  circumstances. 

Fold  a  small  filter  of  about  4  c.  m.  diameter,  put  it  in  an 
air  bath  and  dry  at  110°C  for  15  minutes  —  remove  to  the 
balance  and  weigh  it  rapidly  to  the  nearest  milligram,  do  not 
u  swing  "  the  balance  but  simply  weigh  at  a  standstill. 

Place  trje  paper  in  a  small  funnel,  filter  and  transfer 
the  precipitate  to  it.  This  may  be  done  more  rapidly  if  the 
clear  liquid  be  first  drawn  off  by  a  small  siphon  or,  as  can 
be  done  by  a  little  practice,  with  a  pipette,  so  as  to  leave  but 
a  few  cc  of  liquid  above  the  precipitate,  if  care  be  taken  not 
to  disturb  the  precipitate,  there  is  no  loss  whatever,  and  the 
filtering  of  30  or  40cc  of  liquid  can  be  avoided.  Wash  the 
precipitate  carefully  with  water  containing  1%  of  HNO3  (six 
times  at  least)  set  the  funnel  and  contents  in  an  air  bath  and 
dry  at  110°  to  120°C  30  minutes  after  all  visible  moisture  has 
disappeared.  Then  remove  to  the  balance  and  weigh  rap- 
idly as  before.  The  difference  between  the  second  weight 
and  the  first  gives  the  weight  of  the  yellow  precipitate,  and 
this  in  grammes  gives  the  phosphorus  in  per  cents. 


30  Notes  on  Metallurgical  Analysis. 

Process  for  Iron  and  Steel. — Weigh  1.63  grammes  of  the 
well  mixed  borings  into  a  4-inch  covered  dish  or  caserole, 
add  cautiously  35cc  HNO3  sp.  gr.  1.2  boil  to  dryness,  then 
"bake"  on  a  hot  iron  plate  at  200°C  for  thirty  minutes. 
Take  up  by  heating  with  20cc  HC1,  then  proceed  exactly  as 
in  the  case  of  ores. 

Many  steels  will  dissolve  without  residue  —  of  course  in 
this  case  filtration  of  the  HC1  solution  is  unnecessary. 

The  above  methods  assume  that  the  phosphorus  all  passes  into 
solution  and  that  arsenic  is  absent.  Titaniferous  and  arsenical  ores  and 
metals  for  this  reason  must  be  treated  by  the  first  method,  fortunately 
they  are  the  exception. 

Many  devices  have  been  proposed  for  shortening  this  standard 
method — such  as  employing  wet  methods  of  oxidation  —  to  avoid 
baking  and  evaporation.  Before  adopting  any  one,  it  must  be  carefully 
tested  against  standard  methods  on  the  kind  of  metals  the  chemist  has 
to  work  with,  and  only  used  so  far  as  it  is  thus  proved  adaptable.  Thus 
Mr.  Wood,  at  Homestead,  uses  chromic  acid,  with  the  nitric  acid  for 
solution  and  does  not  bake.  See  Blair  Chem.  Anal.  Iron  and  Steel,  2d 
edition,  p.«102. 

VOLUMETRIC   METHODS. 

Determination  of  phosphorus  in  iron  ore,  iron  and  steel 
by  precipitation  as  Phospho  molybdate,  and  determination  of 
the  amount  of  the  precipitate  by  estimating  the  molybdic 
acid  it  contains  volumetrically,  either  by  potassium  perman- 
ganate after  reduction  by  zinc,  or  by  neutralizing  with  stan- 
dard alkali. 

TITRATION  BY  PERMANGANATE  —  "EMMERTON'S   METHOD." 

When  the  yellow  precipitate  is  dissolved  in  NH4HO,  and  then 
mixed  with  a  very  considerable  excess  of  H2SO4  it  all  remains  in  solu- 
tion. If  this  solution  be  treated  warm  with  metallic  zinc,  the  zinc  rap- 
idly dissolves,  hydrogen  being  given  off  and  the  "molybdic  acid" 
MoO3  is  rapidly  reduced,  giving  a  dark  red  and  finally  olive  green  solu- 
tion containing  what  would  be  if  the  reduction  were  complete,  Mo2O3, 
but  which  appears  to  be  in  fact  Moj  20: 9.  Now,  if  to  this  solution,  after 
being  rapidly  filtered  from  the  undissolved  zinc,  a  solution  of  perman- 
ganate of  potassium  be  added,  the  Mo12O19  is  instantly  reoxidized. 


Notes  on  Metallurgical  Analysis.  31 

The  solution  becomes  colorless,  and  finally,  when  oxidation  is  complete, 
a  drop  of  permanganate  in  excess  gives  a  permanent  pink  tint. 

While  there  is  some  uncertainty  as  to  the  nature  of  the  oxide  pro- 
duced by  reduction,  this  possibly  being  different  for  different  workers, 
it  is  proved  by  the  extensive  use  of  the  method  that  working  always  in 
exactly  the  same  way,  the  reduction  is  uniform,  and  hence,  the  titration 
is  a  reliable  method  for  estimating  the  yellow  precipitate,  and  indirectly 
the  amount  of  phosphorus. 

Consult  a  paper  by  F.  A.  Emmerton,  Trans.  Am.  Inst.  Min.  Engrs., 
vol.  XV,  p.  93. 

Process  of  Analysis — Preparation  of  the  Solution  of 
Permanganate. — Assuming  the  reaction  between  the  oxi- 
dizing agent  and  the  reduced  solution  of  the  yellow  precipi- 
tate to  be  Mo12O19  +  O17  (from  the  permanganate)  =  12 
MoO3,  and  that  the  yellow  precipitate  contains  24  MoO3  to 
1  of  P2O5,  as  is  now  undisputed,  there  must  be  17  atoms 
of  oxygen  furnished  by  the  permanganate  to  oxidize  the  re- 
duced molybdous  acid  equivalent  to  one  atom  of  P  in  the 
yellow  precipitate. 

As  it  is  difficult  to  weigh  out  permanganate  and  dissolve 
it  without  change,  it  is  necessary  to  make*  up  the  solution  of 
approximate  value  and  then  determine  its  strength.  This 
is  easily  done  by  titrating  against  a  solution  containing  iron. 

Two  atoms  of  iron,  asFeO,  require  one  atom  of  oxygen 
to  change  them  to  Fe2O3  ;  hence,  34  atoms  (=2X17); 
of  iron  as  ferrous  salt  will  consume  as  much  oxygen  from 
permanganate  as  will  the  reduced  molybdic  acid,  equivalent 
to  one  atom  of  P  in  the  yellow  precipitate. 

One  atom  of  phosphorus  =  31  —  34  atoms  of  iron  = 
1904  ( 56  X  34 ) ;  hence,  31 : 1904  =  1 :  61.41 ;  that  is,  ^  of 
the  amount  of  iron  to  which  the  permanganate  solution  is 
equivalent  will  give  the  amount  of  phosphorus  to  which  it 
is  equivalent  when  titrating  yellow  precipitate  as  above. 

One  molecule  of  K2Mn2O8  furnishes  five  atoms  of  free 
oxygen  on  reduction ;  hence,  to  furnish  17  atoms  of  oxygen 
as  above  3f  molecules  of  permanganate  are  required  which 
will  be  the  amount  equivalent  to  one  atom  of  phosphor- 
us in  the  above  process. 


32  Notes  on  Metallurgical  Analysis. 

The  molecule  of  K2Mn2O8=316,  3f  times  this  equals 
1,074,  the  amount  equivalent  to  one  atom  =  31  of  phos- 
phorus; or  34.6  parts  by  weight  of  permanganate  will  be 
equal  to  one  of  phosphorus  to  be  determined. 

Therefore,  to  make  a  solution  of  permanganate,  of  which 
Ice  shall  be  equivalent  to  .0001  gram,  of  phosphorus,  or  to 
0.01  per  cent,  when  one  grm.  of  substance  is  taken;  dissolve 
3.46  grms.  of  the  salt  in  water  and  dilute  to  one  litre. 

Allow  the  solution  to  stand  some  time  before  using,  as 
its  strength  is  liable  to  change  at  first,  but  gradually  becomes 
nearly  constant.  Finally  determine  its  value  exactly,  first 
against  pure  ammonium  ferrous  sulphate,  and  second,  against 
a  sample  of  steel  in  which  the  amount  of  phosphorus  has 
been  exactly  and  repeatedly  determined  by  the  magnesia 
process. 

To  standardize  against  the  iron  salt  dissolve  0.8597 
grms.  of  the  Fe  (NH4)2  (SO4)2  6  H2O  in  200cc  of  water 
containing  a  little  H2SO4;  add  the  permanganate  solution 
from  a  burette  until  the  last  drop  gives  a  permanent  pink 
tint  and  then  take  the  reading. 

This  amount  of  the  iron  salt  contains  0.12282  grms.  of 
iron,  which  will  reduce  as  much  permanganate  as  would  be 
equivalent  to  .002  grams,  phosphorus ;  therefore,  20cc  of  the 
solution  should  be  required.  If  more  or  less  is  taken,  cal- 
culate the  amount  of  phosphorus  to  which  Ice  is  equivalent 
by  the  proportion  20  :  n  =  .0001  :  x,  n  being  the  amount 
used  and  x  the  value  sought. 

The  determination  of  the  value  against  a  known  steel  is 
desirable,  as  it  gives  a  result  which  is  independent  of  all 
assumptions  as  to  the  nature  of  the  oxide  produced  by  the 
zinc  reduction. 

Treatment  of  the  Samples  of  Iron  or  Steel. — Weigh  five 
grms.  of  steel  or  one  to  five  grms.  of  iron,  according  to  the 
amount  of  phosphorus ;  put  it  into  a  4  in.  dish  or  caserole,  add 
25  to  75cc  of  HNO3  1,  2  sp.  gr.  Add  the  acid  cautiously  to 
avoid  boiling  over.  After  action  has  ceased  cover  well  and 


Notes  on  Metallurgical  Analysis.  33 

boil  down  dry,  then  bake  on  a  hot  plate  30  minutes,  then  add 
20  to  40cc  cone.  HC1.  Heat  till  all  the  iron  oxide  is  dissolved, 
then  boil  down  to  15cc,  being  careful  to  avoid  the  formation 
of  any  dry  crusts  on  the  side.  This  is  accomplished  by  keep- 
ing the  dish  well  covered  and  shaking  it  around  in  the  hand 
a  little. 

Now  add  20  to  40cc  cone.  HNO3,  washing  off  the  cover 
with  it  into  the  dish.  Boil  down  again  to  10  or  15cc.  It  is 
essential  that  no  dry  iron  salt  form  on  the  sides.  This  is 
easily  avoided  by  covering  with  an  inverted  watch  glass  a 
little  smaller  than  the  dish,  so  that  the  condensed  acid  will 
flow  down  the  sides  and  keep  them  clean.  Cool  slightly, 
moving  the  liquid  around  so  as  to  dissolve  any  crusts  of  fer- 
ric nitrate  formed.  Now  add  30  to  50cc  of  water  and  filter 
into  a  400cc  Erlenmeyer  flask.  The  volume  should  be  about 
75-100cc.  Steels  do  not  require  filtration  as  a  rule. 

Now  add  NH4HO  until  the  ferric  hydrate  separates  and 
the  mass  becomes  thick  and  smells  of  ammonia.  Then  add 
gradually  strong  HNO4,  until  the  precipitate  redissolves  and 
the  liquid  has  a  clear,  amber  color,  not  the  least  red.  The  vol- 
ume should  now  be  about  250cc,  if  not,  dilute  to  that  amount, 
then  put  a  thermometer  in  the  liquid  and  raise  the  temper- 
ature to  85°C.  Now  add  at  once  40cc  of  molybdic  acid  solu- 
tion. Close  the  flask  with  a  rubber  stopper,  wrap  it  in  a 
thick  cloth  and  shake  violently  for  five  minutes. 

This  violent  agitation,  combined  with  the  high  temper- 
ature, causes  the  yellow  precipitate  to  separate  at  once  in  a 
particularly  dense  and  easily  filtered  form. 

At  the  end  of  this  time  let  settle  an  instant,  then  un- 
cork the  flask  and  filter  off  the  solution,  using  a  9  c.  m.  filter. 
Wash  flask  and  precipitate  thoroughly  with  dilute  HNO3 
( 2  per  cent).  Now  set  the  funnel  in  the  flask  and' dissolve  the 
precipitate  back  into  it  with  dilute  ammonia  (1:4)  using 
not  to  exceed  30cc.  Finally  wash  the  filter,  using  as  little 
water  as  possible.  To  save  time  some  chemists  puncture  the 
filter  and  wash  the  precipitate  through  with  water.  Then 


34  Notes  on  Metallurgical  Analysis. 

wash  the  funnel  with  ammonia,  then  with  water.  Now  add 
80cc  of  dilute  H2SO4  (one  part  in  four),  and  then  ten  gram- 
mes of  pulverized  zinc,  which  must  be  free  from  much  iron. 
Now  warm  till  rapid  effervescence  ensues  and  heat  gently 
ten  minutes.  At  the  end  of  this  time  reduction  will  be  com- 
plete. Meanwhile  fold  a  1 2  c.  m.  filter  in  "  ribs ;"  put  it  in 
a  funnel,  and  as  soon  as  the  reduction  of  the  MoO3  is  com- 
plete pour  the  liquid  off  of  the  residue  of  the  zinc  into  the 
filter,  receiving  the  filtrate  in  a  white  china  dish,  rinse  the 
flask  and  zinc  once  with  water,  pour  this  on  the  funnel  after 
the  liquid  has  run  through,  then  fill  up  once  with  water  and 
let  that  run  through.  Thin  filter  paper  must  be  used,  so 
that  the  whole  operation  of  filtration  and  washing  the  zinc 
shall  occupy  but  three  or  four  minutes. 

Now  run  the  permanganate  into  the  dark  colored  filtrate 
till  the  color  is  discharged,  and  the  last  drop  gives  a  faint 
pink  tint,  marking  the  close  of  the  reaction. 

There  is  always  some  impurity  in  the  zinc,  hence  it  is 
absolutely  essential,  to  make  a  blank  test  using  the  30cc  of 
NH4HO,  the  10  grms.  of  zinc  and  80cc  of  sulphuric  acid  as 
before  but  omitting  the  yellow  precipitate.  The  filtrate  in 
this  case  will  always  require  a  small  amount  of  permanganate, 
which  must  be  determined,  and  deducted  from  the  amount 
consumed  in  the  regular  determination,  the  difference  being 
the  permanganate  solution  equivalent  to  the  yellow  pre- 
cipitate. 

The  number  of  cubic  centimeters  of  permanganate  solu- 
tion used,  after  correction  for  error  of  standard,  divided  by 
the  number  of  grammes  of  metal  taken  will  give  the  amount 
of  phosphorus  in  hundredths  of  a  per  cent. 

In  working  this  process  it  is  important  to  check  it  from  time  to 
time  upon  material  similar  to  that  to  be  analyzed,  and  in  which  the 
phosphorus  has  been  determined  gravimetrically. 

Notes  on  Above. — This  is  the  original  process  of  Emmerton  and  has  been  the  starting  point 
of  a  large  number  of  modifications  which  increase  the  speed.  The  whole  process  depends  upon 
such  a  nice  adjustment  of  conditions  that  any  of  these  methods  before  being  adopted  must  be 
worked  by  a  number  of  chemists  and  tried  by  much  experience.  Some  of  them  are  very  highly 
recommended  and  are  undoubtedly  accurate  where  used,  whether  they  would  be  safe  to  adopt  gen- 
erally more  experience  must  determine.  The  above  process  has  been  in  use  some  years  and  proved 


.     Notes  on  Metallurgical  Analysis.  35 

satisfactory,  still  it  should  be  carefully  checked  against  standard  gravimetric  methods,  from  time 
to  time. 

Among  the  important  modifications  advocated  are  the  following  : 

1.     Use  of  wet  methods  of  oxidation  to  save  baking. 

Drown.—  Trans.  Inst.  Min.  Engrs.,  vol.  XVIII,  p.  90— uses  permanganate  and  HNO3  of 
1.135  Sp.  gr.,  which  dissolves  silica.  Does  not  evaporate  to  dryness. 

Shinier. — Trans.  Inst.  Min.  Engrs.,  vol.  XVII,  p.  100 — uses  permanganate  w/ith  sulphuric 
acid.  Evaporating  until  the  HNOs  is  expelled. 

Clemens  Jones. — Trans.  Inst.  Min.  Engrs.,  vol.  XVIII,  p.  705 — uses  the  method  of  Drown, 
but  slightly  modified,  also  washes  the  yellow  precipitate  with  (NH4)2  SO^  solution  to  avoid  the 
presence  of  nitrates. 

Babbitt. — Jour.  An.  and  App.  Chem.,  vol.  VII,  p.  165 — advocates  the  temperature  of  25°C 
instead  of  85°,  to  prevent  the  precipitation  of  arsenic. 

Clemens  Jones  Jour.  Trans.  Inst.  Min.  Engs.,  vol.  17,  p.  411,  performs  the  reduction  of  the 
MoOs  by  filtration  through  zinc. 

Other  papers  of  importance  are  by  Cheever,  Trans.  Inst.  Min.  Engs.,  vol.  14,  p.  372,  and  a 
note  from  Stahl  u.  Eisen  in  Jour.  Soc.  Chem.  Inds.,  vol.  11,  p.  845. 

The  titration  process  may  be  applied  to  ores.  These  should  be  dis- 
solved in  HC1.  Care  must  be  taken  to  destroy  all  organic  matter,  as  this 
may  adhere  to  the  yellow  precipitate  and  cause  reduction  of  the  per- 
manganate. 

Evaporate  the  HC1  solution  with  HNO3,  bake  and  then  follow 
Emmerton.  The  writer's  experience  has  been  that,  while  good  results 
were  obtained  with  many  ores,  with  some  the  process  seemed  to  fail. 

The  titration  method  may  be  applied  to  estimating  the  yellow  pre- 
cipitate obtained  as  described  in  the  direct  weighing  process,  but  the 
"  shake  down  "  method  is  the  most  rapid. 

Titration  of  the  yellow  precipitate  by  standard  alkali. — This  method 
appears  good  for  iron  containing  only  small  percentages  of  phosphorus. 
It  may  be  found  described  in  the  following  papers : 

Jour.  An.  and  App.  Chem.,  vol.  VI,  p.  82. 

Jour.  An.  and  App.  Chem.,  vol.  VI,  p.  204. 

Jour.  An.  and  App.  Chem.,  vol.  VI,  p.  242. 

Zeitschrift  fur  Anal.  Chem.,  vol.  XXVIII,  p.  171. 

A  *'  mechanical"  process  has  been  used  by  which  the  yellow  pre- 
cipitate is  separated  in  a  centrifugal  machine  and  its  amount  measured 
in  a  graduated  tube.  The  results  can  hardly  be  very  exact.  See  Jour. 
An.  and  App.  Chem.,  vol.  IV.  p.  13. 


TUB  DETERMINATION  OF  SILICON  IN  IRON. 

The  metals  in  which  silicon  has  most  frequently  to  be  determined 
are  pig  iron,  containing  from  one-half  to  four  or  five  per  cent.  '*  ferro 
silicon,"  containing  up  to  14  per  cent,  or  more,  steel,  with  from  traces  to 
one-fourth  per  cent.,  and  wrought  iron  with  small  fractions  of  a  per 
cent. 

In  all  these  the  silicon  exists  as  Si,  not  as  SiO2,  though  there  may 
be  a  little  SiO2  included  as  intermixed  slag,  especially  in  wrought  iron. 


36  Notes  on  Metallurgical  Analysis. 

All  of  these  are  easily  soluble  in  HNO3,  1.2  sp.  gr.,  except  ferro 
silicon,  the  Si  being  oxidized  to  SiO2,  part  of  which  passes  into  solution. 
Evaporation  of  the  HNO3  solution  to  dryness,  baking  and  re-solution  in 
HC1  only  partially  renders  this  SiO2  insoluble. 

To  accomplish  the  complete  separation  of  the  SiO2  by  this  means 
it  is  necessary  to  dissolve  the  metal  in  1.2  sp.  gr.  HNO3.  Evaporate  to 
dryness,  bake  as  in  the  phosphorus  determination,  dissolve  in  HC1,  and 
again  evaporate  to  complete  drymss,  expelling  all  the  HC1.  On  taking 
up  again  in  HC1  the  SiO2  is  all  left  insoluble.  After  dilution  the  solu- 
tion may  be  filtered  from  the  residue  of  SiO2  +  C.  This,  after  thorough 
washing  first  with  HC1  and  then  with  water,  may  be  ignited  till  the 
carbon  is  burned  off,  and  weighed. 

The  SiO2  thus  obtained  is  never  pure,  and  must  be  treated  by 
H2SO4  and  HF1,  or  must  be  fused  and  the  SiO2  determined.  (  See  anal- 
ysis of  limestones. ) 

Hydrochloric  acid  or  aqua  regia  may  be  used  in  place  of  HNOs,  but  they  do  not  attack 
ordinary  iron  so  rapidly.  Finally,  solution  in  H2SO4  and  evaporation  till  fumes  of  H2SO4  are 
given  off  has  been  used. 

For  details  of  these  various  methods  see — 

Blair,  Chem.  Anal.  Iron  and  Steel  2d  Ed.,  p.  72,  nitric  acid  method. 

Troilus,  Notes  on  Chem.  of  Iron,  p.  35,  sulphuric  acid  method. 

Also  Trans.  Inst.  Mining  Engineers,  vol.  X,  p.  162  et  seq  and  187  et  seq, 

When  a  solution  containing  SiO2  is  evaporated  with  H2SO4  this 
will  expel  all  volatile  acids,  and  if  the  temperature  is  finally  raised  to 
near  the  boiling  point  of  the  concentrated  acid,  the  silica  is  complete- 
ly dehydrated  and  becomes  insoluble.  Titanic  acid  if  present  passes  into 
solution  and  the  silica  thus  obtained  is  pure.  The  following  method, 
slightly  modified  from  one  published  by  Dr.  Drown,  depends  upon  this 
fact. 

Trans.  Am.  Inst.  Min.  Engrs.,  vol.  VII,  p.  346. 

In  preparing  the  drillings  for  analysis  great  care  must  be  taken  to 
keep  them  free  from  sand.  This  is  very  difficult  in  the  case  of  pig  iron, 
hence  it  is  always  safer  to  clean  them. 

This  is  easily  accomplished  by  folding  a  sheet  of  paper  over  a  mag- 
net, then  picking  up  the  metal  against  the  paper.  The  sand  and  other 
foreign  particles  are  left  behind.  On  drawing  the  magnet  away  from 
the  paper  the  drillings  will  fall  off  and  can  be  collected  on  a  clean  sheet 
of  paper.  All  the  drillings  must  be  gone  over  and  no  considerable  resi- 
due should  remain,  if  much  graphite-like  substance  is  separated  it  may 
hold  silicon  belonging  in  the  sample. 

The  drillings  should  be  fine,  large  fragments  of  metal  dissolved 
slowly  and  may  be  left  as  hard  grains  in  the  silica,  of  course  vitiating 
the  result. 

If  these  lumps  remain,  add  more  acid  and  heat  slowly  until  they 
dissolve. 

In  u  weighing  out "  great  care  must  be  taken  to  secure  an  average 
of  fine  and  course,  as  these  usually  differ  in  per  cent,  of  silicon. 


Notes  on  Metallurgical  Analysis.  37 

Process  for  Pig  Iron  and  Steel. — Weigh  1  grm.  of  pig 
iron  or  5  grins,  of  wrought  iron  or  steel.  Put  into  a  caserole 
or  dish  and  cover  with  a  large  watch  glass.  Add  carefully 
30cc  of  a  cold  mixture  of  8  parts  by  volume  of  cone.  HNO3, 
5  parts  of  cone.  H2SO4  and  17  parts  of  H2O  (for  1  grm.  of  pig 
iron)  or  lOOcc  of  a  mixture  of  35  parts  of  cone.  HNO3,  15 
parts  of  H2SO4  and  50  parts  of  H2O  (for  5  grms.  of  steel). 

Warm  till  action  ceases,  then  boil  down  rapidly  on  an 
iron  plate  or  over  the  bare  flame  until  the  Fe2  (SO4)3  sepa- 
rates as  a  white  mass ;  continue  the  heating  until  dense 
fumes  of  H2SO4  are  evolved.  These  have  a  peculiar  suffo- 
cating odor,  easily  recognized  ;  their  formation  indicates  the 
total  expulsion  of  the  HNO3.  This  is  absolutely  necessary 
in  order  to  make  the  silica  insoluble.  There  will  be  danger 
of  u  spattering  "  unless  the  heating  be  carefully  done,  but  if 
the  dish  be  well  covered  this  need  cause  no  loss. 

Now  let  cool,  and  then  wash  off  the  cover  into  the  dish. 
Dilute  to  150  or  200cc,  cover,  set  over  a  lamp  and  boil 
until  all  Fe2  (SO4)3  is  dissolved,  as  can  be  recognized  by  the 
disappearance  of  the  silky  precipitate  in  the  liquid.  Continue 
the  boiling  for  five  minutes.  Wash  off  the  cover,  then  let 
the  liquid  stand  until  all  the  SiO2  settles,  Decant  the  clear 
liquid  through  a  7  c.  m.  ashless  filter,  previously  washed  out 
with  boiling  water.  Finally  transfer  and  wash  the  residue 
with  hot  water.  When  partially  washed,  drop  a  little 
HC1  on  the  filter  and  residue  then  wash  again  with  hot 
water  till  the  filtrate  no  longer  tastes  acid.  Without  drying 
transfer  the  filter  to  a  crucible  and  ignite,  gently  at  first, 
finally  at  high  heat,  until  all  the  carbon  (graphite)  is  burned 
and  the  SiO2  is  white.  If  this  be  done  in  a  platinum  cruci- 
ble and  over  a  blast  lamp  the  "  burning  off"  of  the  carbon 
need  not  take  more  than  a  few  moments.  It  may  be  much 
hastened  by  directing  a  very  gentle  current  of  oxygen  gas 
into  the  crucible.  If  care  be  taken  not  to  blow  out  any  of 
the  light  particles  of  SiO2,  this  is  a  good  plan.  The  weight 
of  the  SiO2,  multiplied  by  0.4667,  gives  the  Si. 


38  Notes  on  Metallurgical  Analysis. 

If  the  above  directions  are  exactly  followed  as  to  diluting  and  boil- 
ing the  solution  after  evaporation,  there  will  be  no  need  of  a  filter  pump 
to  secure  rapid  filtration.  Boiling  with  a  large  excess  of  water  consoli- 
dates the  SiO2  so  it  filters  easily. 

In  the  case  of  steels,  the  SiO2  being  very  small  in  amount,  it  is  nec- 
essary to  test  its  purity.  Add  a  drop  of  H2SO4,  and  then  either  a  few 
drops  of  pure  HF1  or  a  few  crystals  of  pure  NH4  Fl.  Evaporate  to  dry- 
ness  and  ignite  strongly.  The  SiO2  goes  off  as  gaseous  SiFl4.  The 
residue,  if  any  remains,  is  to  be  deducted  from  the  total  weight,  the  dif- 
ference being  SiO2. 

At  the  Edgar  Thomson  Steel  Works  a  special  process  for  Si  in  pig 
iron  is  used.  They  chill  the  iron  in  water  which  makes  it  brittle.  This 
is  then  pulverized  in  a  steel  mortar,  dissolved  in  HC1,  rapidly  evaporated 
to  dryness,  taken  up  in  HC1,  diluted  and  filtered.  Without  drying,  the 
residue  is  put  into  a  platinum  crucible,  ignited  in  a  stream  of  oxygen 
and  weighed.  The  time  is  said  to  be  12  minutes.  Of  course  it  is  not 
very  exact. 

For  details  see  Blair  Chem.  Anal,  iron  and  steel ;  second  edition,  p.  77. 

Determination  of  Siliconin  Ferro  Silicon. — This  material  is  not  easily 
attacked  by  any  of  the  above  mixtures.  It  can  usually  be  dissolved  by 
prolonged  boiling  with  aqua  regia,  adding  fresh  acid  from  time  to  time. 
Finally  add  25cc  of  dilute  (1:3)  H2SO4,  evaporate  until  fumes  of  SO3  ap- 
pear, and  then  finish  as  in  the  regular  process. 

Those  samples  which  aqua  regia  will  not  dissolve  are,  according  to 
Williams,  best  treated  by  fusing  with  6  or  8  times  the  weight  of  dry 
Na2CO3.  Then  proceeding  with  the  fusion,  as  in  the  determination  of 
SiO2  in  the  insoluble  matter  of  a  limestone.  The  metal  must  be  very 
finely  pulverized  and  not  more  than  0.5  grm.  taken. 

Williams.     Trans.  Am.  Inst.  Min.  Engrs.,  vol.  XVII,  p.  542. 

TUB  DBTBR-MINAXIO^  OF  MANGANBSB. 

Two  classes  of  substance  present  themselves.    First,  ores,  slags  and       ., 
metals  high  in  manganese,  such  as  manganese  ore  and  ferro  manganese, 
with  from  15  to  90  per  cent,  of  manganese;  second,  ordinary  iron  ores, 
irons  and  steels,  with  from  a  trace  to  about  3  per  cent,  of  manganese. 

THE   ACETATE   PROCESS,    FOR  THE   DETERMINATION  OF 
MANGANESE   IN    ORES   WITH   HIGH   PERCENTAGES. 

The  process  depends  upon  the  separation  of  the  iron  and  alumina 
as  basic  acetates,  precipitation  of  the  Mn  by  bromine,  re-solution  and 
determination  as  pyrophosphate. 

When  a  solution  of  Fe2Cl6  and  MnCl2  is  boiled  with  sodium  or 
ammonium  acetate,  the  iron  is  precipitated  completely,  provided,  first, 
the  solution  is  sufficiently  dilute,  containing  less  than  one  gram.  Fe2O3 


Notes  on  Metallurgical  Analysis.  39 

in  500cc  ;  second,  the  amount  of  free  acid  is  very  small.  This  precipitate 
is  nearly  free  from  manganese,  provided  the  excess  of  acetate  of  soda  is 
very  small.  If  bromine  water  is  added  to  the  filtrate,  the  Mn  is  com- 
pletely precipitated  as  MnO2,  provided  a  considerable  excess  of  sodium 
acetate  is  present.  If  ammonium  salts  are  present,  the  MnO2  will  only 
separate  when  the  solution  is  made  alkaline.  The  iron  solution  must 
contain  no  ferrous  salt  or  a  red  ''  brick  dust "  like,  slimy  precipitate  will 
form,  and  the  filtrate  will  be  cloudy  and  deposit  iron. 

The  process  is  perfectly  satisfactory  provided  all  details  are  very 
carefully  attended  to. 

Process  for  Ores. — Dissolve  one-half  grm.  of  the  ore  in 
15cc  concentrated  HC1,  dilute  and  filter  as  in  the  iron  assay. 

Evaporation  to  dryness  is  usually  unnecessary,  few  ores  containing 
soluble  silicates.  When  such  occur,  as  in  slags,  dissolve  in  dilute  acid, 
evaporate  to  dryness,  add  HC1  and  then  water. 

If  no  chlorine  is  given  off  when  the  ore  is  dissolved,  owing  to  the 
absence  of  MnO2,  ferrous  iron  may  be  present.  In  this  case  add  a  crystal 
of  KC1O3  and  boil  until  all  the  Cl  is  expelled. 

When  a  ferric  chloride  solution  is  evaporated  to  dryness  in  the 
presence  of  organic  matter  a  slight  reduction  to  ferrous  salt  often  occurs  ; 
hence,  in  this  case  always  oxidize  the  solution  after  filtration  by  adding 
a  little  KC1O3  or  HNO3.  The  solution  must  be  boiled  till  all  the  Cl  is 
expelled  or  Mn  will  precipitate  with  the  iron  in  the  subsequent  sep- 
aration. 

See  Blair  Chem.  An.  Iron,  page  227. 

To  the  filtrate  add  a  solution  of  sodium  carbonate  care- 
fully until  a  slight  permanent  precipitate  forms.  Redissolve 
this  with  a  few  drops  of  HC1,  giving  each  drop  two  or  three 
minutes  to  act,  and  stopping  as  soon  as  the  solution  clears. 

Now  dilute  to  about  300cc,  add  one  grm.  sodium  ace- 
tate, cover  the  beaker  and  boil  vigorously  till  the  iron  separates. 
Should  it  not  come  down  promptly  drop  in  a  solution  of 
Na2CO3  drop  by  drop  until  the  precipitation  is  complete.  The 
liquid  tested  by  a  slip  of  litmus  paper  must  be  distinctly 
acid.  Let  the  precipitate  settle  clear  and  decant  the  liquid 
through  a  9  c.  m.  filter  as  close  as  possible,  add  150cc  of  boil- 
ing water,  settle,  pour  off  and  finally  run  the  precipitate  on 
to  the  filter  and  wash  once  with  hot  water.  Wash  it  off 
the  filter  back  into  the  beaker.  Dissolve  it  in  its  least  pos- 
sible quantity  of  HC1  and  repeat  the  precipitation  exactlv  as 


40  Notes  on  Metallurgical  Analysis. 

before.     Transfer  the  precipitate  to  the  filter  and  wash  well 
with  hot  water. 

Test  this  last  precipitate  for  Mn  by  fusing  with  Na2CO3 
and  NaNO3  on  a  platinum  wire.  If  not  free  from  Mn  a  third 
precipitation  will  be  necessary. 

The  filtrate  will  amount  to  about  a  litre.  It  should  be 
perfectly  clear  and  colorless.  Concentrate  it  to  about  500cc, 
then  add  ten  grms.  of  sodium  acetate  and  an  excess  of  bro- 
mine water.  Warm  until  the  MnO2  has  settled  and  the 
liquid  is  clear.  Filter  on  to  a  7  c.  m.  filter  and  wash  well 
with  hot  water. 

Wash  the  precipitate  off  the  filter  into  a  beaker.  Now 
wash  the  filter  paper  with  dilute  HC1,  in  which  a  small  crys- 
tal of  oxalic  acid  is  dissolved.  This  will  dissolve  off  all  adher- 
ing MnO2.  Heat  the  HC1  containing  the  MnO2  in  the  beaker, 
adding  oxalic  acid  solution  drop  by  drop  until  the  MnO2  is  all 
dissolved.  Now  dilute  to  150cc,  and  add  NH4HO  till  a  slight 
permanent  precipitate  is  formed,  then  a  few  drops  of  acetic 
acid  and  boil.  If  any  precipitate  of  Fe2O3  separates  filter  it 
off  and  wash  it. 

Unless  this  is  light  red  in  color  and  very  small  in  amount,  redis- 
solve  it  in  a  few  drops  of  HC1,  add  H2O,  then  NH4HO,  then  acetic  acid 
as  before.  Boil  till  the  precipitate  separates  and  filter  into  the  original 
solution.  This  re-solution  is  essential  in  most  cases,  and  need  delay  the 
work  but  a  few  moments.  The  object  of  the  oxalic  acid  is  to  reduce 
the  MnO2  to  MnO,  and  so  make  it  dissolve  quickly.  MnO2  is  very 
slowly  attacked  by  dilute  HC1. 

To  the  filtrate,  now  perfectly  clear  and  colorless,  add  an 
excess  of  a  solution  of  microcosmic  salt  ( Na2NH4PO4).  Now 
heat  to  boiling,  add  NH4HO  drop  by  drop  as  fast  as  the  pre- 
cipitate formed  by  each  addition  becomes  u  silky  "  in  appear- 
ance, stirring  all  the  time  to  prevent  bumping.  When  no 
more  precipitate  forms  add  enough  NH4HO  to  make  the  solu- 
tion smell  slightly  of  NH3,  and  boil  till  the  precipitate  is  com- 
pletely silky  and  settles  quickly.  Now  cool  the  liquid  and 
filter.  Wash  the  precipitate  with  water  containing  a  few 
drops  of  NH4HO.  Ignite,  weigh  as  Mn2P2O7,  containing 
0.3874  manganese. 


Notes  on  Metallurgical  Analysis.  41 

The  acetate  of  soda  used  must  be  tested  for  Mn.  If  any  is  found, 
dissolve  the  salt  in  water,  add  bromine  water  and  boil  till  all  the  bro- 
mine is  expelled.  Filter  the  solution  from  the  MnO2  thus  separated 
and  use  it  instead  of  the  solid  salt. 

Process  for  Spiegle  Iron  and  Ferro^  Manganese. — Take 
one-half  gram,  of  the  drillings,  dissolve  in  lOcc  HNO3 
1.2  sp.  gr.,  evaporate  to  dryness  and  "  bake,"  then  dissolve 
in  lOcc  cone.  HC1,  add  a  little  bromine  water  ( to  reoxidize 
any  FeO  formed ),  boil  down  till  all  excess  of  bromine  is 
gone  and  most  of  the  HC1  evaporated.  Dilute,  filter  if  nec- 
essary; precipitate  the  iron  and  determine  the  Mn  as  by  the 
method  for  ores. 

Some  ores  and  spiegle  irons  contain  copper  and  nickel.  These  will 
come  down  with  the  MnO2  in  part  at  least.  They  should  be  separated 
by  H2S,  which  will  precipitate  Ni,  Co.  Cu.  and  Zn.,  but  not  Mn  from  a 
solution  containing  a  slight  excess  of  acetic  acid. 

This  may  be  done  in  the  original  acetate  fiitrate.  The  solution 
must  be  boiled  till  all  H2S  is  expelled  before  adding  bromine. 

THE   ACETATE   PROCESS   FOR   IRON   ORES   CONTAINING 
BUT   LITTLE   MANGANESE. 

In  this  case  it  is  desirable  to  work  upon  larger  amounts  of  material. 
The  filtration  and  washing  of  a  large  basic  acetate  precipitate  is  very 
troublesome,  and  can  be  avoided  by  taking  an  aliquot  part  of  the  solu- 
tion after  the  precipitate  has  settled. 

The  error  introduced  by  the  bulk  of  the  precipitate  is  inappreciable 
when  the  per  cent,  of  manganese  is  small. 

A  single  precipitation  of  the  iron  is  entirely  sufficient,  provided 
care  be  taken  to  avoid  excess  of  sodium  acetate. 

Extreme  care  in  measuring  the  solution,  as  well  as  in  keeping  the 
temperature  constant,  is  also  superfluous  where  under  three  per  cent,  of 
manganese  is  present  and  the  volumes  are  kept  large,  as  lOcc  on  a  litre 
could  only  cause  an  error  of  0.03  per  cent. 

The  precipitate  by  bromine  is  MnO2.  On  ignition  it  changes  to 
Mn3O4,  but  only  when  ignited  under  very  exact  conditions  as  to  tem- 
perature and  access  of  air.  This  precipitate  also  usually  retains  small 
amounts  of  soda  salts.  For  these  reasons  the  percentage  of  Mn  it  con- 
tains will  always  be  a  little  uncertain. 

However,  as  these  variations  are  limited  to  a  small  percentage  of  the 
weight  of  the  precipitate,  the  results  obtained  by  direct  weighing,  where 
but  little  Mn  is  present,  will  be  sufficiently  accurate  for  all  ordinary  work. 

Process. — Dissolve  four  grms.  of  the  ore  in  30cc  cone. 
HC1  exactly  as  in  the  iron  assay.  If  there  is  any  ferrous 


42  Notes  on  Metallurgical  Analysis. 

iron  present  add  about  Ice  of  HNO3  to  completely  convert  it 
to  ferric  chloride.  Boil  the  solution  until  all  chlorine  and 
excess  of  HNO3  are  expelled.  The  evaporation  must  not  go 
so  far  that  insoluble  iron  salts  separate ;  should  such  form 
add  more  HC1  and  heat  until  they  dissolve.  Add  water, 
warm  and  filter  from  the  residue. 

Take  a  large  Erlenmeyer  flask,  one  which  will  hold 
when  quite  full  2400cc.  Dry  it,  then  measure  into  it  exactly 
2000cc  of  water ;  this  should  reach  up  into  the  narrower  por- 
tion of  the  flask.  Paste  a  thin  strip  of  paper  on  the  glass  to 
exactly  indicate  the  level  of  the  liquid.  The  flask  must  be 
set  on  a  level  desk,  and  the  place  it  stands  as  well  as  the  po- 
sition of  the  paper  mark  noted,  so  that  it  can  be  subse- 
quently returned  to  the  same  position. 

Now  transfer  the  solution  of  the  ore  to  the  flask  and  di- 
lute it  to  about  1700cc.  Then  add  a  solution  of  Na2CO3 
gradually  until  the  liquid  begins  to  grow  dark  red.  Con- 
tinue to  add  the  reagent  drop  by  drop,  shaking  the  flask  after 
each  addition  until  the  liquid  is  very  dark  in  color  and  the 
precipitate  formed  only  redissolves  slowly.  The  object  is  to 
reach  a  point  just  short  of  that  at  which  the  iron  will  be 
precipitated.  The  operation  requires  practice.  Should  the 
point  be  overstepped,  add  a  little  HC1,  and  when  the  liquid 
becomes  clear,  neutralize  over  again ;  but  in  this  case,  in 
the  writer's  opinion,  the  iron  precipitate  is  more  liable  to 
contain  Mn. 

Now  add  six  grms.  of  pure  sodium  acetate.  Set  the 
flask  on  a  hot  plate  and  boil  the  solution  hard. 

The  iron  should  immediately  separate  as  a  bulky,  red 
precipitate.  If  it  fails  to  do  so  at  once  drop  in  very  cau- 
tiously a  dilute  solution  of  Na2CO3  until  the  separation  is 
complete.  Now  boil  a  few  minutes  longer,  then  remove  the 
flask  to  the  place  where  it  stood  when  graduated,  placing  it 
in  the  same  position,  and  fill  it  exactly  to  the  mark  with 
cold  water.  With  a  long  rod  stir  the  liquid  thoroughly,  then 


Notes  on  Metallurgical  Analysis.  43 

let  it  settle.  As  soon  as  it  is  clear  pour  off  one  litre  into  a 
graduated  flask.  This  whole  operation  can  be  done  so 
quickly  that  the  liquid  will  not  cool  materially. 

Filter  the  measured  portion  of  the  liquid.  The  filtrate 
should  be  colorless  and  distinctly  acid  to  litmus  paper. 

Concentrate  the  filtrate  to  about  500cc.  Add  five  grms. 
of  sodium  acetate  and  boil.  Should  any  precipitate  form  fil- 
ter it  off,  dissolve  it  in  HC1  containing  a  little  oxalic  acid, 
add  a  solution  of  Na2CO3  until  a  slight  permanent  precipitate 
forms,  then  acetic  acid  till  just  acid.  Boil  this  liquid,  filter 
from  any  precipitate,  and  add  the  filtrate  to  the  main 
solution. 

Finally  add  bromine  water,  warm  until  the  MnO2  settles 
completely,  filter,  wash  well  with  hot  water,  ignite  and  weigh 
as  Mn3O4  containing  0.7205  Mn.  Calculate  the  result  as 
though  two  grms.  of  ore  had  been  taken. 

Should  the  ore  leave  little  residue  it  need  not  be  filtered  off,  but 
may  go  into  the  flask  with  the  solution.  In  applying  this  process  to 
slags  and  ores  containing  decomposable  silicates,  the  HC1  solution  must 
be  evaporated  to  dryness,  taken  up  again  in  HC1,  HNO3  added  and 
boiled  off  as  usual. 

If  care  be  taken  in  the  neutralizing  no  precipitate  will  form  on  con- 
centrating the  filtrate  from  the  iron  and  delay  will  be  avoided. 

Should  the  ore  contain  nickel  or  copper,  these  will  contaminate  the 
manganese  precipitate  and  the  results  will  be  inaccurate.  In  this  case 
the  precipitate  of  MnO 2  must  be  redissolved  in  HC1  containing  a  little 
sodium  sulphite.  The  solution  boiled  till  free  from  SO2  and  then  cooled 
and  nearly  neutralized  by  Na2CO3,  a  little  sodium  acetate  added  and  the 
Ni  and  Cu  precipitated  by  H2S.  In  the  filtrate  from  these  su]phides  the 
Mn  can  be  determined  either  by  precipitation  with  bromine  or  as  phos- 
phate. 

The  Acetate  Process  may  be  Applied  to  Pig  Iron  and  Steel.  —  Dis- 
solve 4  grms.  in  50cc  HNO3  1.2  sp.  gr.,  add  lOcc  cone.  HC1.  Evaporate 
todryuess  and  "bake."  Redissolve  in  25cc  cone.  HOI,  add  a  little  HNO3 
boil  and  proceed  as  with  ores  low  in  manganese.  Filtration  from  the 
insoluble  residue  is  unnecessary  in  this  case. 

References  on  the  acetate  process  : 

Blair — Chem.  Anal.  Iron,  Second  Ed.,  p.  103,  et.  seq.,  also  p.  227. 

Jour.  Soc.  Chem.  Indst.,  vol  X,  p    101,  on  the  properties  of  Mn3O.j. 

Trans.  Inst.  Min.  Engrs.,  vol  X,  p.  101. 

Gibbs— Sillimans  Am.  Jour.  [11]  44,  p.  216,  on  the  determination  as  phosphate. 


44  Notes  on  Metallurgical  Analysis. 

THE  POTASSIUM  CHLORATE,  OR  FORD — WILLIAMS*  METHOD 

FOR  MANGANESE. 

This  is  a  volumetric  method  depending  upon  the  precipitation  of 
the  Mn  asMnO2  by  KC1O3  from  a  solution  in  concentrated  HNO3,  and 
after  filtering  off  and  washing  the  MnO2  determining  it  volumetrically 
by  measuring  its  oxidizing  power. 

See  Trans.  Am.  Inst.  Min.  Engrs.,  vol.  IX,  p.  397— Ford. 
Trans.  Am.  Inst.  Min.  Engrs.,  vol.  X,  p.  100— Williams. 
Trans.  Am.  Inst.  Min.  Engrs.,  vol.  XII,  p.  73— Troilus. 
Trans.  Am.  Inst.  Min.  Engrs.,  vol.  XIV,  p.  372— Cheever. 

The  method  is  especially  adapted  to  the  determination  of  man- 
ganese in  steels  and  irons  low  in  silicon  and  dissolving  in  HNO3  without 
residue. 

When  KC1O3  is  added  in  successive  small  portions  to  a  boiling  hot 
solution  of  Mn  in  concentrated  HNO3,  the  Mn  is  completely  and  rapidly 
precipitated  as  MnO2,  provided  an  amount  of  iron  at  least  equal  to  the 
Mn,  be  present,  HC1  be  absent  and  the  HNO3  in  sufficiently  large  excess 
and  sufficiently  concentrated. 

This  MnO2  is  entirely  insoluble  in  cold  concentrated  HNO3  pro- 
vided this  contains  no  lower  oxides  of  nitrogen  (  "  red  fumes  ") ;  if  these 
are  present,  that  is  if  the  HNO3  is  not  perfectly  colorless,  the  MnO2  will 
be  reduced  and  dissolved. 

The  precipitate  contains  a  little  iron  but  is  free  from  other  im- 
purities. 

When  the  solution  to  be  precipitated  by  KC1O3  contains  any  HC1, 
this  will  be  first  acted  upon  and  destroyed  before  the  MnO2  will  separate. 
Chlorine  being  driven  off  and  water  formed  by  the  oxidation.  This  will 
result  in  a  weakening  of  the  HNO3,  and  hence  in  this  case  more  HNO3 
must  be  present  to  prevent  too  great  loss  of  strength. 

SiO2  in  the  solution  may  separate  in  a  gelatinous  form  and  prevent 
filtration,  hence  it  must  always  be  first  removed. 

Chlorate  Process  for  Steel  Low  in  Silicon  —  Precip- 
itation of  the  MnO%. —  Dissolve  5  grrns.  in  60cc  1.2  HNO3,  in 
a  No.  2  beaker.  Evaporate  down  to  25cc,  then  add  lOOcc 
of  colorless  cone.  HNO3.  Set  on  an  iron  plate  and  heat 
to  incipient  boiling.  Now  drop  in  powdered  KC1O3,  a 
little  at  a  time,  adding  each  portion  when  the  effervescence 
from  the  preceding  portion  has  ceased.  By  the  time  2  to 
2^  grms.  have  been  added  the  MnO2  will  have  separated  as 
a  fine  brown  powder.  Now  add  j£  grm.  more  KC1O3  and 
boil  gently  for  10  minutes.  Then  add  1  grm.  more  KC1O3 
and  25cc  cone.  HNO3  and  boil  10  minutes  longer.  Remove 
from  the  plate  and  cool  by  setting  in  water.  When  the  MnO2 


Notes  on  Metallurgical  Analysis.  45 

has  settled,  filter  without  dilution,  through  an  asbestos  filter,1 
finally  run  the  MnO2  on  the  filter  and  wash  beaker  and  filter 
with  colorless  concentrated  HNO3  three  or  four  times.  This 
can  be  done  without  using  more  than  15  or  20cc,  adding  only 
a  little  each  time  and  letting  each  portion  run  through  before 
adding  the  next.  Finally  wash  with  a  little  cold  water.  If 
the  HNO3is  colored  by  lower  oxides  of  nitrogen  (from  stand- 
ing and  the  action  of  light),  it  may  be  purified  by  blowing  a 
strong  current  of  air  through  it  for  some  time,  until  colorless. 

After  washing  the  MnO2  with  cold  water  till  the  acid 
taste  is  gone  from  the  filtrate,  (letting  each  successive  por- 
tion of  water  run  entirely  through  before  adding  the  next,  so 
as  not  to  use  in  all  more  than  20cc)  wash  the  asbestos  and 
precipitate  back  into  the  beaker  (which  will  always  have 
some  MnO2  adhering  to  it),  and  proceed  with  the  volumetric 
determination  of  the  manganese. 

Volumetric  Determination  of  the  Mn  O2. — 

This  process  consists  in  dissolving  the  MnO2  in  a  measured  excess  of 
an  acid  solution  of  ferrous  sulphate  of  a  known  strength  Each  mole- 
cule of  MnO2  changes  two  molecules  of  ferrous  sulphate  to  ferric  sul- 
phate. The  amount  of  ferrous  sulphate  remaining  is  then  determined 
by  a  standard  solution  of  potassium  permanganate.  The  reactions  are 
as  follows : 

1.     MnO2  4-  2  FeSO4  +  2  H2SO4  =  MnSO4  -f  Fe2  (SOJ  3  +  2  H2Q. 

2.— 10FeSO4  +  K2  Mn2  O8  +  8H2SO4  =  5Fe2  (SO4)3  +  K2SO4  + 
2  MnSO4  -f  8  H2O. 

In  all  work  involving  the  use  of  potassium  permanganate  only  glass 
stoppered  or  Gay  Lussac  burettes  must  be  used,  as  it  is  reduced  and  de- 
stroyed by  contact  with  all  organic  materials,  such  as  rubber  tubes,  paper, 
etc.  There  are  required,  first,  a  solution  of  potassium  permanganate  of  a 
known  strength ;  second,  a  solution  of  ferrous  sulphate  in  dilute  sul- 
phuric acid.  The  strength  of  this  is  determined  by  titration  with  the 
permanganate  solution. 

Preparation  of  the  Permanganate  Solution. — Dissolve 
1.149  grms.  of  pure  potassium  permanganate  in  water  and 

1.  To  Prepare  the  Asbestos  Filter. —  Melt  the  bottom  of  a  six-inch  test  tube  and  draw  it 
out  into  a  narrow  tube.  Cut  off  the  end  and  into  the  long  funnel  thus  formed  drop  a  little  disc  of 
platinum  foil  punched  full  of  holes  and  fastened  to  a  wire  which  can  run  into  the  funnel  stem  and 
hold  the  foil  in  place.  Then  put  in  a  little  asbestos  which  has  been  boiled  with  HC1,  washed  and 
finally  ignited  in  a  platinum  crucible.  Do  not  "  pack  "  it  in,  simply  pour  on  water  and  let  it  run 
through  so  as  to  settle  it  on  the  bottom.  By  a  little  practice  a  filter  can  be  made  in  this  way  which 
will  work  rapidly  and  yet  retain  all  the  MnO  2 . 


46  Notes  on  Metallurgical  Analysis, 

dilute  to  one  litre.  Ice  of  this  solution  will  have  the  same 
oxidizing  power  as  0.001  gram,  of  manganese  in  the  form  of 
the  brown  precipitate  (MnO2).  Check  the  solution  against 
pure  iron  or  pure  ammonium  ferrous  sulphate  (NH4)2  Fe 
(SO4)2  6  H2O.  Dissolve  0.1425  grins,  of  the  salt  in  50cc  of 
water  containing  2cc  of  H2SO4.  This  should  consume  just 
lOcc  of  the  permanganate  solution.  Run  in  the  solution 
until  the  last  drop  gives  a  permanent  pink  color. 

If  more  or  less  than  lOcc  is  required,  calculate  the 
amount  of  Mn  to  which  each  cc  of  the  permanganate  is 
equivalent  by  the  proportion. 

.001  :  x  —  n  :  10,  n  being  the  number  of  cc  of  solution 
used  in  the  test,  and  x  the  required  value. 

Preparation  of  the  Ferrous  Sulphate  Solution. — Dis- 
solve 20.18  grms.  of  pure  crystallized  ferrous  sulphate 
(FeSO47H2O)  in  about  500cc  of  water,  to  which  25cc  of  con- 
centrated H2SO4  has  been  added,  and  then  dilute  to  one  litre. 

Determine  its  strength  against  the  permanganate  solu- 
tion by  measuring  5cc  with  a  pipette  into  a  beaker,  adding 
about  25cc  of  water  and  then  running  in  the  permanganate 
till  the  pink  color  is  permanent.  About  lOcc  should  be  required . 

This  value  must  be  redetermined  frequently  as  the  solu- 
tion of  ferrous  sulphate  alters  rapidly  from  the  oxidizing 
action  of  the  air. 

In  a  large  way  it  is  best  kept  in  a  carboy  and  covered 
with  a  layer  of  kerosene  oil  to  keep  out  air. 

The  solution  can  be  drawn  out  by  a  siphon,  and  when 
used  in  this  way  alters  less  rapidly. 

From  the  two  formulas  already  given  we  have  the  relations  between 
the  MnO2,  FeSO4  and  K2Mn2O8  as  follows : 

One  atom  of  Mn  in  the  form  of  brown  precipitate  (MnO2 )  will  oxidize 
2  atoms  of  Fe  as  ferrous  sulphate.  1  molecule  of  permanganate  will 
oxidize  10  atoms  of  Fe  as  ferrous  sulphate,  that  is  to  say  one  molecule 
of  permanganate  will  oxidize  the  same  amount  of  iron  as  will  5  mole- 
cules of  MnO2  containing  5  atoms  of  manganese. 

Therefore  to  find  how  much  K2Mn2O8  will  be  needed  to  have  the 
same  oxidizing  power  as  0.001  grms.  of  Mn  in  the  form  of  the  brown 
precipitate  we  have  the  proportion. 


Notes  on  Metallurgical  Analysis.  47 

Wt.  5  atoms  Mn  :  wt.  1  mol.  K2Mn2O8  =275  :  316  =.001  :  x,  which 
gives  #=.001 149  grms.,  the  amount  of  K2Mn2O8  to  be  dissolved  in  Ice 
if  Ice  is  to  be  equivalent  to  .001  grm.  Mn  as  "brown  precipitate."  This 
is  1.149  grms.  in  a  litre. 

To  determine  the  amount  of  iron,  or  of  ammonium  ferrous  sul- 
phate to  which  Ice  should  be  equivalent,  we  have, 

Wt.  1  atom  Mn  :  Wt.  2  atoms  Fe  =  55 :  1 12  =.001 :  x,  in  which  x  is  the 
required  amount  of  iron.  The  value  of  x  is  0.002034.  To  determine  the 
amount  of  the  am.  fer.  sulph.,  as  this  contains  \  of  its  weight  of  iron, 
multiply  the  value  of  x  by  seven  .-.=.01425  for  Ice,  or  the  figure  given 
in  the  directions  for  making  the  check  for  lOcc. 

That  5cc  of  the  ferrous  sulphate  solution  may  be  equivalent  to  lOcc 
of  the  permanganate  it  must  contain  0.02034  Fe.  This  corresponds  to 
20.18  grms.  of  Fe  SO3  7  H2O  to  the  litre. 

Determination  of  the  MnO2. — To  the  asbestos  and  MnO2 
in  the  beaker,  add  the  solution  of  ferrous  sulphate  from  a 
pipette  5cc  at  a  time  until,  after  stirring  and  warming,  the 
MnO2  is  completely  dissolved.  It  is  best  to  take  the  same 
pipette  used  in  standardizing.  Break  up  all  lumps  of  asbestos 
or  precipitate  with  a  glass  rod  as  they  may  conceal  undissolved 
particles  of  MnO2.  Now  add  a  little  water  and  run  in  the 
permanganate  solution  till  a  permanent  pink  color  is  pro- 
duced (it  may  disappear  in  two  or  three  minutes,  but  this  is 
of  no  consequence).  Read  the  burette  and  deduct  the 
amount  used  from  that  to  which  the  amount  of  ferrous  sul- 
phate taken  would  have  been  equivalent  —  the  difference  is 
that  equivalent  to  the  Mn  present  in  the  precipitate.  This, 
corrected  by  the  factor  for  the  permanganate  solution  will 
give  the  amount  of  Mn  in  milligrams. 

As  an  example — Suppose  that  See  of  ferrous  sulphate  solution 
equaled  9.6cc  of  permanganate  solution,  and  10.3cc  permanganate 
equaled  0.1425  grms.  of  ammonium  ferrous  sulphate.  If  15cc  of  ferrous 
sulphate  solution  was  added  to  dissolve  the  MnO2  and  the  permanganate 
required  to  oxidize  the  excess  was  4.5cc,  then  the  calculation  would  be 
as  follows : 

3  X  9.6  =  28.8  =  the  permanganate  equivalent  to  the  fer.  sulph.  used. 
4.5  =  the  "Titre  back." 

24.3  =  the  number  of  cc  of  permanganate  equivalent  to 
the  precipitate. 

24.3 :x  =  10.3:10  (x  being  the  true  amount  of  correct  permanganate). 

re  =  23.6  =  0.0236  grms.  Mn  in  the  precipitate. 


48  Notes  on  Metallurgical  Analysis. 

THE   CHLORATE    PROCESS  FOR   ORES. 

Take  5  grms.  dissolve  in  50cc  of  cone.  HC1.  Evaporate  to  dryness, 
avoiding  a  temperature  above  100°,  add  20cc  HC1,  and  then  water. 
When  dissolved  filter  into  a  No.  2  beaker.  Add  oOcc  cone.  HNO3, 
evaporate  to  a  syrup,  then  add  lOOccof  cone.  HNO3  and  proceed  as  before. 

THE  CHLORATE  PROCESS  FOR  PIG  IRON. 

Dissolve  5  grms.  of  the  metal  in  HNO3  1.2  sp.  gr.,  taking  about 
60cc.  Then  add  25cc  HC1,  evaporate  to  dryness  and  bake.  Dis- 
solve in  HC1,  filter  from  the  SiO2,  and  to  the  filtrate  add  0.2  grm.  am- 
monium fluoride  or  a  few  drops  of  hydrofluoric  acid.  Then  add  50cc  of 
HNO3.  Concentrate  to  a  syrup,  add  lOOcc  HNO3  and  proceed  as  before. 
The  hydrofluoric  acid  expels  traces  of  SiO2  from  the  solution  and  greatly 
accelerates  the  filtration  from  the  MnO2.  (E.  F.  Wood.) 

The  above  process,  carefully  conducted,  gives  very  accurate  results, 
but  it  should,  be  checked  against  metals  in  which  theMn  has  been  care- 
fully determined  by  the  acetate  method  until  the  two  work  together. 

For  Ferro  Silicon  and  Ores  high  in  Manganese. — The  permanganate 
solution  should  be  standardized  by  working  on  a  metal  of  known 
percentage  of  Mn,  as  the  composition  of  the  precipitate  is  considered  by 
some  chemists  not  to  be  exactly  MnO2,  and  by  thus  standardizing  in  the 
same  way  that  the  ore  is  analyzed  all  risk  from  this  source  is  avoided. 
Where  only  small  amounts  of  Mn  are  present  this  source  of  error  is  un- 
important. 

The  acetate  process  is  probably  better  adapted  to  all  high  manga- 
nese materials,  and  if  skillfully  worked  is  nearly  as  rapid  as  the  other 
when  HC1  has  to  be  expelled  by  evaporation  with  HNO3. 

One  slight  objection  to  the  chlorate  process  is  the  large  amounts  of 
expensive  acids  required. 

To  avoid  this  the  process  can  be-  worked  on  smaller  amounts  of 
substance,  but  great  care  and  skill  is  then  needed  to  secure  close  results. 
All  measurements  and  titrations  muse  be  very  exact. 

Take  one  grm.  of  iron  or  steel,  dissolve  it  in  15cc  of  HNO3  1.2  sp. 
gr.  Evaporate  to  lOcc,  add  35cc  HNO3,  and  after  precipitation  and 
boiling  lOcc  more,  cutting  down  the  KC1O3  to  about  one  grm.,  filter, 
wash  and  proceed  with  the  volumetric  determination  of  the  precipitate. 

COLOR  PROCESS   FOR   MANGANESE. 

This  depends  upon  the  change  of  Mn  to  permanganic  acid  when 
boiled  in  nitric  acid  solution  with  PbO2. 

It  is  sufficiently  accurate  for  steels,  irons  and  ores  when  the  amount 
of  Mn  is  small,  provided  exactly  the  same  manipulation  is  adhered  to 
in  every  case. 


Notes  on  Metallurgical  Analysis.  49 

It  requires,  first,  a  "standard  material  containing  a  known  amount 
of  Mil,  of  approximately  the  same  per  cent,  as  the  material  to  be  tested, 
and  of  precisely  the  same  kind  (steel  for  steel  and  pig  iron  for  pig  iron, 
ore  for  ore,  etc.).  Second,  PbO2  free  from  Mn. 

The  method  is  usually  restricted  to  steels,  but  may  be  used  with 
certain  modifications  for  an  approximate  estimate  of  the  Mn  in  ores  and 
pig  iron  containing  very  small  amounts. 

Process  for  Steel. — Dissolve  0:2  grms.  of  steel  in  a  test 
tube  in  15cc  HNO3  1.2  sp.  gr.  Cover  with  a  small  glass 
bulb  and  heat  in  a  water  bath  until  solution  is  complete. 
Now  filter  if  necessary,  dilute  to  lOOcc  aud  mix.  Put  ICcc 
of  this  solution  in  an  8-inch  test  tube,  add  3cc  HNO3  1.2  sp. 
gr.,  heat  till  the  solution  boils  rapidly.  (This  is  best  done 
by  setting  the  tube  in  a  CaCl2  bath,  boiling  at  115°C.)  Now 
add  carefully  while  boiling  0.5  grms.  PbO2  and  continue  to 
boil  for  exactly  five  minutes.  The  tube  must  be  covered  all 
the  time  by  a  little  glass  bulb,  or  dry  iron  salts  will  form  on 
the  sides. 

Now  set  the  tube  vertically  in  cold  water  and  let  settle 
till  the  PbO2  is  all  on  the  bottom  and  the  violet  liquid  is  ab- 
solutely clear.  Avoid  exposure  to  bright  light,  which  may 
change  the  color.  There  must  have  been  prepared  at  the  same 
time  and  in  the  same  way  a  solution  of  the  standard  steel. 
Pour  off  the  two  solutions  into  two  "  carbon  tubes  "  and  di- 
lute till  the  color  "  matches."  The  volumes  will  then  have 
the  same  ratio  as  the  amounts  of  manganese  in  the  standard 
and  the  test  sample. 

To  Apply  this^Process  to  Pig  Iron. — Dissolve  0.2  grms.  in  5cc  of  HC1 
of  1.1  sp.  gr.  (1 : 2)  and  filter  the  solution,  evaporate  it  to  a  syrup  with 
lOcc  cone.  HNO3,  add  5cc  more,  dilute  and  proceed  as  with  steel. 

In  the  Case  of  Ores. — Dissolve  0.2  grin,  in  5cc  of  HC1  and  boil  to  a 
syrup,  add  lOcc  cone.  HNO3,  evaporate  to  a  syrup,  add  lOcc  HNO3  1.2 
sp.  gr.,  dilute,  filter  and  proceed  as  before. 

References  on  the  Color  Process — 

Blair  Chem.  Anal.  Iron  and  Steel,  2d  Ed.,  p.  120. 
Hunt  Trans.  Am.  Dist.  Min.  Engrs.,  vol.  15,  p.  164. 

Numerous  other  methods  are  in  use  for  Mn.  Chief  among  these 
is  Volhard's  method,  titrating  the  Mn  in  the  filtrate  after  separating  the 
iron  by  ZnO. 

See  Blair  Chem.  Anal.,  2d  Ed.,  p.  112. 

The  titration  is  difficult  except  for  an  expert. 


50  Notes  on  Metallurgical  Analysis. 

THE  DETERMINATION  OF*  SUUPHUR. 

Sulphur  occurs  in  iron  ores,  both  in  the  form  of  sulphides,  such  as 
pyrites  (FeS2)  and  as  sulphates,  such  as  gypsum  (CaSO42H2O),  or  occa- 
sionally barite  (BaSO4). 

In  iron  and  steel  the  sulphur  is  entirely  in  the  form  of  sulphide. 

In  all  gravimetric  methods  the  sulphur  is  first  entirely  converted 
into  some  soluble  sulphate,  and  then  determined  by  precipitation  with 
barium  chloride  as  barium  sulphate  (BaSO4). 

In  order  to  be  satisfactory  the  precipitation  must  be  done  under 
carefully  regulated  conditions. 

Barium  sulphate,  while  entirely  insoluble  in  water,  is  not  so  in  di- 
lute acids,  the  amount  dissolved  increasing  with  the  concentration  of 
the  acid.  The  presence  of  a  considerable  excess  of  BaCl2  in  the  liquid 
appears,  however,  to  counteract  this  solvent  action.  Thus  a  sufficient 
excess  of  BaCl2  will  completely  precipitate  the  sulphuric  acid  from  a 
solution  strongly  acid  with  HC1. 

When  BaSO4  is  precipitated  in  solutions  containing  much  iron, 
basic, iron  salts  will  adhere  to  the  precipitate,  making  it  reddish  in  color 
unless  the  solution  contains  considerable  excess  of  HC1.  This  color  is 
shown  best  after  the  precipitate  is  ignited.  Some  of  the  sulphuric  acid 
appears  to  be  in  combination  with  this  iron,  and  is  driven  off  on  igni- 
tion, leaving  ferric  oxide  ;  so  that  these  impure  precipitates  are  liable  to 
give  low  results,  particularly  if  subsequently  purified  and  the  BaSO4  they 
contain  determined. 

Barium  salts,  particularly  the  nitrate  (Ba(NO3)2)  have  a  strong 
tendency  to  adhere  to  the  precipitate,  making  it  impure ;  these  cannot  be 
completely  washed  out  with  water. 

Acid  solutions  of  Fe2Cl6  when  hot,  hold  a  little  BaSO4  in  solution, 
this  separates  completely  when  the  liquid  cools.  The  precipitate  of 
BaSO4  is  fine,  liable  to  run  through  the  filter  and  impure,  when  precip- 
itated cold,  or  in  concentrated  solutions  or  by  too  concentrated  a  solution 
of  BaCl2.  This  last  point  is  especially  important.  The  solution  of 
BaCl2  must  always  be  well  diluted  and  heated  to  boiling  before  being 
added.  Working  in  this  way  will  give  a  granular,  rapidly  subsiding 
precipitate  easy  to  wash  and  pure. 

See  Fres.  Quant.  Anal.,  §  71  (a).     Archbutt  — Jour.  Soc.  Chem.  Inds.,  9,  p.  25. 
Lunge  —  Jour.  Soc.  Chem.  Inds.,  8,  p.  967 ;  also  a  note  in  the  same  Journal,  8,  p.  819. 

Conversion  of  the  Sulphides  to  Sulphates. — All  sulphides  are  com- 
pletely oxidized  to  sulphates  when  fused  with  a  mixture  of  dry  Na2CO3 
and  NaNO3. 

As  certain  bisulphides  give  off  sulphur  vapor  at  a  comparatively 
low  temperature  (below  the  fusing  point  of  Na2CO3),  when  these  or  free 
sulphur  are  present  care  must  be  taken  to  prevent  loss  in  this  way. 
The  mixture  of  ore  and  flux  must  be  covered  with  a  layer  of  pure 
"  fusion  mixture"  and  heated  carefully. 


Notes  on  Metallurgical  Analysis.  51 

After  fusion  all  the  sulphur,  whether  originally  present  as  sul- 
phides or  sulphates  (including  BaSO4)  will  be  found  as  Na2SO4,  the 
other  bases  remaining  as  oxides  or  carbonates.  When  the  fused  mass  is 
boiled  with  water  till  thoroughly  disintegrated  and  then  filtered  and 
washed  the  sulphur  all  passes  into  the  filtrate. 

Sulphides  can  be  more  or  less  completely  oxidized  to  sulphates  in  the 
"wet  way"  by  treating  them  with  hot  concentrated  HNO3  or  aqua 
regia.  These  methods  are  not  very  satisfactory,  as  free  sulphur  is  liable 
to  separate  and  fuse  in  drops.  Once  in  this  form  it  resists  boiling  with 
all  ordinary  oxidizing  agents  for  a  long  time.  Iron  sulphides  can  be 
completely  oxidized  by  boiling  with  a  large  excess  of  concentrated  HNO3 
and  adding  a  little  powdered  KC1O3. 

When  iron  sulphides,  or  even  iron  containing  but  little  sulphur,  is 
dissolved  in  dilute  (1.2  sp.  gr.)  HNO3  a  considerable  amount  of  the  sul- 
phur separates  as  such  and  escapes  oxidation. 

Solutions  containing  sulphuric  acid,  on  evaporation  todrynessand 
"baking,"  as  is  common  in  iron  analysis,  may  loose  SO3  unless  enough 
potash  or  soda  be  present  to  hold  it  all  in  combination,  as  the  sulphates 
of  iron  are  easily  decomposed  by  heat. 

See  Fresenius  —  Quant.  Anal.  §148,  2. 
Blair  — Chem  Anal.  Iron,  p.  66  and  p.  220. 

Method  for  Sulphur  in  Iron  Ores. — Mix  one  grm.  of  the 
finely  pulverized  ore  with  eight  grms.  of  dry  Na2CO3  and  one- 
half  to  one  grm.  of  NaNO3,  according  to  the  amount  of  sul- 
phur in  the  ore.  Put  the  mixture  in  a  platinum  crucible 
and  fuse  carefully.  As  soon  as  it  is  well  melted  chill  the 
crucible  by  dipping  the  bottom  in  water.  Boil  out  the 
fusion  with  water  until  all  the  material  is  soft  and  no  hard 
lumps  remain,  and  if  the  solution  is  colored  by  Mn2Na2O8, 
add  a  few  drops  of  alcohol.  Filter  and  wash  well  with  hot 
water.  Add  HC1  to  the  filtrate  till  just  acid,  and  evaporate 
it  to  dry  ness  carefully,  and  dry  at  100°C.  Now  add  5cc  of 
HC1  first  diluted  with  its  own  volume  of  water.  Warm  and 
add  50cc  of  H2O,  heat  till  all  is  dissolved  but  a  little  SiO2, 
filter  and  wash.  The  filtrate  should  not  exceed  lOOcc,  if  it 
does  concentrate  it.  Now  heat  to  boiling  and  add  5  to  lOcc  of 
a  10  per  cent,  solution  of  BaCl2  previously  diluted  with  10  or 
20cc  of  water  and  heated.  Stir  and  let  the  precipitate  of 
BaSO4  settle.  When  clear,  filter,  wash  with  hot  water,  dry, 
ignite  and  weigh  as  BaSO4,  the  weight  of  which  multiplied 
by  0.137  =  S. 


52    •  Notes  on  Metallurgical  Analysis. 

BaSO4  is  easily  reduced  to  BaS  by  heating  with  carbon  ;  hence,  in 
igniting  the  precipitate  detach  it  as  tar  as  possible  from  the  filter,  burn 
the  paper  carefully  on  a  platinum  wire,  avoiding  a  high  heat.  Add  the 
ash  to  the  precipitate  in  the  crucible  and  heat  gently  with  the  cover  off 
until  all  carbon  is  burned,  finally  igniting  to  a  bright  red  heat.  After 
weighing  the  precipitate  add  a  little  water  to  it  and  test  with  turmeric 
paper.  If  it  reacts  alkaline  the  results  are  untrustworthy.  Ordinary 
gas  contains  sulphur,  which  forms  SO2  on  burning,  and  is  liable  to  get 
into  sulphur  determination.  Therefore,  keep  the  crucible  well  covered 
during  the  fusion.  In  accurate  work  it  is  always  necessary  to  make  a 
blank  analysis,  and  determine  the  small  amount  of  sulphur  contained 
by  the  reagents  or  absorbed  from  the  gas  flames.  Deduct  this  from  the 
amount  found  when  working  on  the  ore. 

Method  for  Sulphur  in  Iron  and  Steel. — This  is  usually 
present  in  very  small  percentages. 

Take  from  two  to  five  grms.,  according  to  the  per  cent, 
of  sulphur.  Add  from  25  to  40cc  concentrated  HNO3.  Cool 
the  dish  if  the  action  is  too  strong,  or  heat  it  if  too  slow. 
When  nearly  all  is  dissolved,  heat  to  boiling  and  add  2  or 
3cc  cone.  HC1  to  complete  the  solution.  Now  add  about  one- 
half  grm.  KC1O3  free  from  sulphur.  Boil  to  dryness  and  bake 
slightly.  Add  10  to  20cc  cone.  HC1  to  dissolve  it  and  again 
dry  down  thoroughly.  Dissolve  the  residue  in  15  to  40cc 
cone.  HC1.  Evaporate  the  solution  until  a  skin  begins  to 
form  on  the  solution  or  it  becomes  syrupy.  Now  add  5cc. 
of  cone.  HC1.  When  all  dissolves  clear  dilute  with  its  own 
volume  of  hot  water  and  filter  into  a  small  beaker  through 
a  paper  previously  washed  out  with  a  little  hot  dilute  HC1 
(this  facilitates  filtration),  wash  the  dish  and  residue  with 
hot  water. 

The  filtrate  and  washings  must  not  exceed  75cc.  Now 
heat  and  add  5cc  of  a  10  per  cent,  solution  of  BaCl2  and  let 
stand  till  the  liquid  settles  perfectly  clear.  (Two  hours  is 
sufficient  if  everything  is  right.) 

Filter  on  to  a  small  ashless  filter,  wash  with  water  con- 
taining a  little  HC1,  dry,  ignite  and  weigh  as  BaSO4. 

The  residue  from  which  the  solution  for  the  determination  of  sul- 
phur is  filtered  must  contain  no  basic  iron  salts  (due  to  the  great  concen- 
tration before  dilution),  as  these  may  hold  sulphur. 

Jour.  Anal,  and  App.  Chem.,  vol.  6,  p.  318. 


on  Metallurgical  Analysis.  53 

This  nitric  acid  method  may  be  applied  to  ores.  Use  one  grm.  of 
ore,  20cc  HNO3  and  a  little  KC1O3.  Evaporate  to  dryness,  take  up  in 
HC1  and  proceed  as  in  the  treatment  of  iron.  This  process  will  not  de- 
termine the  sulphur  in  any  barium  sulphate,  or  all  that  in  any  lead 
sulphide  present,  and  hence  is  not  so  universally  applicable  as  the  reg- 
ular fusion  method. 

THE     DETERMINATION      OF     SULPHUR     IN     PIG     IRON     AND 
STEEL    BY   EVOLUTION    AS    H2S. 

The  oxidation  methods:  while  accurate,  and  the  only  ones  that  can 
be  relied  upon  to  certainly  give  the  total  sulphur  in  any  material,  are 
slow. 

When  iron  containing  sulphur  is  dissolved  in  HC1,  the  sulphur  is 
evolved  as  H2S.  This  gas  can  be  absorbed  by  various  substances  and 
the  sulphur  determined  volu metrically  or  gravimetrically. 

Several  very  rapid  methods  are  based  on  this  reaction.  They  are 
especially  adapted  to  pig  iron  and  steel  containing  but  small  fractions  of 
a  per  cent,  of  sulphur,  and  when  properly  conducted  are  accurate,  but 
are  subject  to  a  number  of  causes  of  error  which  must  be  carefully 
guarded  against. 

H2S  is  very  easily  decomposed  by  comparatively  feeble  oxidizing 
agents,  water  being  formed  and  free  sulphur  deposited.  Prolonged  con- 
tact with  air  and  sunlight,  solutions  of  Fe2Cl6,  traces  of  chlorine,  all 
act  on  it  in  this  way.  Therefore  all  these  must  be  avoided  in  the  pro- 
cess. There  is  no  necessity,  however,  of  working  in  an  atmosphere  of 
hydrogen  or  CO2  if  the  process  be  rapidly  conducted.  On  the  other 
hand  slow  evolution,  or  HC1  containing  traces  of  Cl  or  Fe2Cl6  will  cause 
retention  of  sulphur  in  the  residue  from  the  solution. 

Dilute  HC1,  according  to  the  writer's  experience,  frequently  fails 
to  cause  complete  evolution  of  the  sulphur  as  H2S  where  the  concen- 
trated acid  succeeds. 

Most  irons  when  dissolved  rapidly  in  hot  concentrated  HC1  free 
from  oxidizing  impurities  leave  a  residue  practically  free  from  sulphur. 

This  residue  should  always  be  examined  for  sulphur,  however,  un- 
less previous  tests  on  the  same  kind  of  metal  have  shown  it  to  be  free,  in 
which  case  this  is  unnecessary.  The  presence  of  copper  or  arsenic  in 
the  metal  would  of  course  have  a  tendency  to  hold  sulphur  behind,  as 
their  sulphides  are  not  decomposed  by  HC1. 

PERMANGANATE,    OR   DROWN*S   METHOD. 

This  is  the  quickest  and  least  troublesome  of  the  gravimetric  evolu- 
tion methods.  It  is  accurate  for  small  percentages  of  sulphur.  A  solu- 
tion of  K2Mn2O8  will  completely  oxidize  a  little  H2S  to  H2SO4,  pro- 
vided the  volume  of  liquid  is  large,  otherwise  free  sulphur  will  separate. 


54  Notes  on  Metallurgical  Analysis. 

Process. — Take  5  or  10  grms.  of  the  borings,  put  them 
in  a  flask  of  500cc  capacity  provided  with  a  funnel  tube  having 
a  stopcock,  and  a  delivery,  tube.  This  latter  should  have  a  bulb 
blown  in  it  and  be  so  inclined  that  any  acid  condensing  in 
the  tube  may  run  back  into  the  flask.  It  is  a  good  plan  to 
jacket  this  tube  with  a  larger  one,  filling  the  space  between 
them  with  water  to  cool  it  and  prevent  free  acid  distilling 
over  into  the  absorption  bottles.  This  delivery  tube  carries 
the  gas  into  a  series  of  three  bottles,  each  having  a  capacity 
of  about  lOOcc,  and  containing  30  to  40cc  of  a  J  per  cent,  so- 
lution of  permanganate  of  potassium. 

Add  to  the  flask  2  or  3  grms.  of  pure  Na2CO3  which  will 
liberate  CO2  on  the  addition  of  the  acid  and  expel  the  air. 

Now  run  in  cautiously  and  little  at  a  time,  50  to  60cc  of 
cone.  HC1.  This  must  be  so  done  as  not  to  cause  too  rapid 
an  evolution  of  gas.  When  the  action  has  become  moderate 
heat  carefully  to  boiling  and  boil  till  steam  condenses  in  the 
tube  and  all  the  iron  is  dissolved,  probably  1  or  2  minutes. 
This  will  drive  all  the  H2S  over  into  the  permanganate 
bottles. 

Be  careful  on  withdrawing  the  lamp  to  let  air  into  the 
flask  by  opening  the  stopcock  of  the  funnel  tube,  or  the 
vacuum  formed  on  cooling  will  draw  the  permanganate  back 
into  the  flask. 

Empty  the  bottles  into  a  beaker,  wash  them  out,  as  well 
as  the  connecting  tubes.  Dissolve  any  MnO2  adhering  to  the 
sides  by  a  little  cone.  HC1,  and  add  it  to  the  permanganate 
solution  in  the  beaker.  Add  in  all  about  lOcc  of  HC1 ;  now 
boil  and  drop  in  a  solution  of  pure  oxalic  acid  until  the  MnO2 
all  dissolves  and  a  clear  solution  remains  (always  look  out  for 
traces  of  unoxidized  sulphur  in  the  liquid,  which,  if  found, 
of  course  vitiate  the  analysis).  Now  add  5cc  of  a  10  per 
cent,  solution  of  BaCl2.  Let  the  precipitate  of  BaSO4  settle. 
Filter,  wash,  ignite  and  weigh. 

Examination  of  the  Residue  in  the  Flask  for  Sulphur.  —  Filter  the 
contents  of  the  flask  on  a  9  c.  m.  filter.  Wash  the  residue  thoroughly 
and  dry  it  rapidly,  but  avoid  heating  it  above  100°C.  Open  out  the 


Notes  on  Metallurgical  Analysis.  55 

filter  and  brush  the  residue  into  a  small  beaker.  Add  lOcc  of  concen- 
trated HNO3  and  a  small  crystal  of  KC1O3.  Boil  down  to  dryness,  take 
up  by  heating  with  5cc  of  cone.  HC1,  dilute  to  30  or  40cc,  filter  and  add 
.5cc  of  Bad 2  solution  to  the  filtrate.  Let  stand  till  any  precipitate  of 
BaSO4  settles,  filter  it  off  and  weigh  it. 

The  residue  may  also  be  treated  by  fusion  exactly  as  an  iron  ore,  of 
course  using  smaller  quantities  of  fluxes. 

Drown — Trans.  Am.  Inst.  Min.  Engrs.,  vol.  II,  p.  224. 

Many  other  absorbents  are  used,  for  details  see  the  following : 

Trans.  Am.  Inst.  Min    Engrs.,  vol.  X,  p.  187.     Cadmium  salts. 
Trans.  Am.  Inst.  Min.  Engrs.,  vol.  XII,  p.  507.     Bromine. 

Blair  —  Chem.  An.  Iron  and  Steel,  p.  59,  et.  seq.,  Lead  and  Silver  salts  and  Peroxide  of 
Hydrogen. 

DETERMINATION   OF   SULPHUR   IN   IRON   AND   STEEL   BY 
TITRATION  WITH   IODINE. 

This  is  a  very  rapid  method.  It  is  in  general  use  and  when  prop- 
erly conducted  gives  satisfactory  results. 

The  gas  from  the  evolution  flask  is  passed  into  a  solution  of  sodium 
or  potassium  hydrate  by  which  the  H2S  is  rapidly  and  completely  ab- 
sorbed, alkaline  sulphide  being  formed.  (2  NaHO  -f-  H2S  =  Na2S  + 
2H20.) 

On  adding  HC1  to  this,  the  H2S  is  again  liberated  (Na2S  -f  2  HC1 
=2  Nad  -H  H2S.)  If  this  be  done  in  the  presence  of  a  large  volume  of 
cold  water,  the  H2S  will  not  escape,  but  will  remain  in  solution  in  the 
water.  This  solution  of  H2S  is  then  titrated  by  a  standard  solution  of 
iodine,  which  unites  with  the  hydrogen,  setting  free  the  sulphur, 
(H28  +  2I  =  2HI  +  S.) 

By  adding  a  little  solution  of  starch  to  the  liquid,  the  least  excess 
of  iodine  is  shown  by  an  intense  blue  color  ("iodide  of  starch"). 

The  liberated  sulphur  causes  the  liquid  to  become  curiously  opa- 
lescent and  show  various  colors,  but  this  does  not  at  all  obscure  the  u  end 
reaction,"  which  is  very  sharp. 

The  solutions  needed  are  standard  iodine  and  starch. 

Preparation  of  the  Starch  Solution. — Mix  about  one 
grm.  of  starch  with  3  or  4cc  of  cold  water  till  all  lumps  are 
gone,  pour  this  slowly  into  about  200cc  of  boiling  water. 
Boil  the  liquid  a  minute  or  two,  then  let  stand  till  cold.  Do 
not  use  it  hot. 

Preparation  of  the  Iodine  Solution. — Weigh  3.968  grms. 
of  pure  resublimed  iodine  on  a  watch  glass.  Put  it  in  a  small 
beaker,  add  about  six  grms.  of  pure  potassium  iodide  (free 
from  iodate)  and  lOcc  of  water.  Let  stand  in  the  cold  until 


56  Notes  on  Metallurgical  Analysis. 

all  the  iodine  dissolves,  then  transfer  to  a  graduated  flask 
and  dilute  to  one  litre. 

One  cubic  centimeter  of  this  solution  should  be  equiv- 
alent to  0.0005  grms.  of  sulphur.  If  five  grms.  of  metal  be 
taken  for  the  analysis  each  cc  of  iodine  solution  consumed 
will  be  equivalent  to  O.OJ  per  cent,  of  sulphur. 

In  the  reaction  H2S  +  2  I  =  2  HI  4-  S,  two  atoms  of  I  are  equiva- 
lent to  one  atom  of  S,  or  254  by  weight  of  I  =  32  of  S.  To  find  the 
amount  of  I,  which  must  be  contained  in  Ice  to  give  a  solution  of  the 
above  value  in  sulphur,  make  the  proportion  .0005  :  x  =  32  :  254,  which 
gives  x  =  .003968,  and  this  amount  in  Ice  will  be  3.968  grms.  per  litre. 

Iodine  is  insoluble  in  water,  but  is  easily  and  rapidly  dissolved  in 
very  concentrated  solutions  of  KI,  though  very  slowly  in  dilute  ones. 

The  iodine  solution  is  not  constant ;  hence,  its  strength  must  be 
determined  frequently. 

Standardising  of  the  Iodine  Solution. — Prepare  the  fol- 
lowing solutions : 

A.  7.75   grms.    crystallized    sodium    hyposulphite  dis- 
solved in  water  and  diluted  to  one  litre. 

B.  0.1536  grms.   of    fused  potassium  bichromate  dis- 
solved in  water  and  diluted  to  lOOcc. 

Measure  with  a  pipette  lOcc  of  solution  A  into  a  beaker, 
add  lOOcc  of  water  and  3  or  4cc  of  starch  solution.  Now 
run  in  the  iodine  solution  from  a  burette  until  the  last  drop 
gives  a  decided  blue  color,  not  disappearing  on  stirring. 
Note  exactly  the  amount  used.  Repeat  this  two  or  three 
times.  The  results  should  agree  almost  exactly.  Take 
their  average  as  the  amount  of  iodine  equivalent  to  lOcc  of 
the  uhypo"  solution. 

Now  measure  in  the  same  way  lOcc  of  solution  B  into  a 
beaker2  add  50cc  of  water  and  then  about  0.5  grms.  of 
pure  KI. 

When  the  KI  is  dissolved  add  5cc  of  cone.  HC1,  which 
must  be  free  from  Cl  or  Fe.  Let  the  mixture  stand  without 
warming  6  or  7  minutes,  (it  will  become  brown  from  the  lib- 
erated iodine)  then  add  lOcc  of  solution  "A,"  and  3  or  4cc  of 
starch  solution.  If  the  liquid  now  has  a  dark  blue  color  add 
lOcc  more  of  solution  A,  which  will  make  it  colorless. 


Notes  on  Metallurgical  Analysis.  57 

Finally  add  the  iodine  solution  carefully  until  the  blue  color 
is  developed.  Note  exactly  the  volume  of  this  solution 
used.  Call  it  R. 

Now  deduct  from  the  amount  of  iodine  solution  which 
would  be  equivalent  to  the  10  or  20cc  of  the  hyposulphite 
solution  used  (solution  A),  this  amount  (R)  and  the  differ- 
ence will  be  the  volume  of  the  iodine  solution  which  is  equiva- 
lent to  Q.Wb  of  sulphur.  Represent  this  by  Q.  Then  -^ 
will  be  the  amount  of  sulphur  to  which  Ice  of  the  solution 
is  equivalent.  To  reduce  any  observed  volume  to  the  true 
value  make  the  proportion  Q  :  10  =  N  :  x,  in  which  x  is  the 
true  volume  of  correct  iodine  solution. 

The  reactions  upon  which  this  process  of  standardizing  depend  are : 

1.  Na2S2O3  5  H2O  -f  2  I  =  2  Nal  -h  Na284O6  -f  5  H2O.      (The 
crystallized  hyposulphite  contains  5  molecules  of  water.) 

2.  K2Cr2O7  -t-  6  KI  +  14  HC1  =  8  KC1  +  Cr2Cl6  -f  7  H2O  -f  6  I. 
The  molecule  of  hyposulphite    weighs    496,   and  as  1   molecule 

"  Hypo."  is  equivalent  to  2  atoms  of  iodine  (254)  we  have  the  proportion 
496  :  254  —  7.75  :  3.968,  7.75  being  the  amount  of  "  Hypo."  dissolved  in  1 
litre  to  give  a  solution  equivalent  to  the  iodine. 

The  ''Hypo."  solution  is  not  very  constant,  hence  cannot  be  used 
as  an  absolute  check  on  the  iodine  solution,  but  only  as  a  means  of  com- 
paring it  with  an  absolutely  known  amount  of  iodine.  This  definite 
amount  of  iodine  is  obtained  from  the  action  of  bichromate  on  an  ex- 
cess of  KI  in  the  presence  of  HC1.  The  reaction  between  KI  and  K2 
Cr2O7  is  not  instantaneous,  but  rapidly  becomes  complete. 

The  relation  between  the  K2O2O7  and  the  I  is  294.5  :  761.1,  hence 
0.01536  K2Cr2O7  will  liberate  0.03968  grins,  of  iodine,  the  amount  which 
should  be  present  in  lOcc  of  the  iodine  solution  of  its  strength  were 
exactly  right. 

The  operation  itself  consists  therefore  in  finding  how  much  of  the 
iodine  solution  to  be  standardized,  is  required  to  titrate  the  amount  of 
the  hypo,  solution  which  is  equivalent  to  exactly  0.03968  grms.  of  iodine, 
as  liberated  by  the  bichromate.  Thus  we  rind  first  how  much  of  the 
iodine  solution  is  equal  to  a  certain  amount  of  the  hypo,  solution  ; 
second,  how  much  of  the  same  iodine  solution  is  equal  to  what  is  left 
after  the  same  amount  of  hypo,  has  been  acted  upon  by  0.03968  grms.  of 
iodine,  and  the  difference  is  obviously  the  amount  of  iodine  solution 
which  contains  0.03968  grms.  of  iodine,  that  is  to  say  will  be  equivalent 
to  0.005  of  S ;  but  this  should  be  lOcc,  hence  the  difference  between  10 
and  the  amount  taken  is  the  amount  the  solution  is  off  the  standard. 

The  only  precautions  to  be  noted  are  the  necessity  of  giving  time 


58  Notes  on  Metallurgical  Analysis. 

for  the  K2Cr2O7  to  react  on  the  KI  and  the  necessity  of  avoiding  heat 
as  iodine  is  readily  volatilized  from  its  solution. 

The  HC1  used  must  be  free  from  all  impurities  which  liberate  iodine 
from  KI  (Cl,  Fe2Cl6,  CuCl2,  etc.). 

The  Iodine  Solution  may  also  be  Standardized  against  a  sample 
of  iron  or  steel  similar  to  that  to  be  analyzed  in  which  the  sulphur  has 
been  accurately  and  repeatedly  determined  by  the  permanganate 
method. 

Put  the  metal  through  the  regular  process  and  thus  determine 
to  just  how  much  sulphur  each  cc  of  the  iodine  solution  is  equivalent. 
Make  a  factor  of  correction  to  apply  to  the  iodine  solution.  This  method 
of  standardizing  has  the  advantage  of  causing  all  errors  of  solution,  evo- 
lution and  oxidation  to  affect  the  standard  and  sample  alike. 

See  Wilson,  Jour.  An.  and  App.  Chem.,  vol.  V,  p.  439. 

The  Process. — Arrange  a  flask  as  in  Brown's  permanga- 
nate method,  except  substitute  for  the  bottles  one  large 
U-tube  and  a  large  test  tube,  into  which  the  connection  tube 
from  the  U-tube  passes,  reaching  nearly  to  the  bottom. 

Put  into  the  U-tube  and  the  test  tube  each  30cc  of  a 
20  per  cent,  solution  of  pure  sodium  or  potassium  hydrate. 

Now  weigh  into  the  flask  five  grins,  of  the  metal  drill- 
ings. Add  cone.  HC1  and  evolve  the  gas  exactly  as  in  the 
other  process,  but  leaving  out  the  Na2CO3,  and  pushing  the 
process  more  rapidly,  as  the  NaHO  will  let  no  H2S  escape, 
even  if  the  evolution  of  gas  is  very  rapid. 

When  the  iron  is  dissolved  and  the  solution  has  been 
boiled,  detach  the  U-tube  and  test  tube.  Empty  and  rinse 
them  into  a  large  beaker  or  dish,  and  add  300  or  400cc  of  cold 
water.  Now  add  enough  HC1  to  make  the  liquid  distinctly 
acid,  then  3  or  4cc  of  the  starch  solution  and  titrate  with  the 
iodine  solution,  adding  it  until  a  drop  changes  the  opalescent 
liquid  to  a  deep  blue,  not  disappearing  on  standing  two  or 
three  minutes. 

If  five  grins,  of  metal  were  taken,  then  the  number  of  cc 
used,  after  correction  for  standard  will  give  the  amount  of 
sulphur  in  hundredths  of  a  per  cent. 

A  blank  test  on  the  NaHO  must  always  be  made,  as  it 
will  usually  consume  a  little  iodine.  This  must  be  deducted 
from  that  used  in  the  analysis. 


Xotes  on  Metallurgical  Analysis.  59 

A  very  simple  method  of  avoiding  calculation  in  this  process  is  to 
take,  instead  of  fivegrms.  of  iron,  ten  times  the  amount  in  grms.  to  which 
the  standardizing  has  shoivn  one  litre  of  the  iodine  solution  to  be  equiva- 
lent in  sulphur.  If  this  is  done  the  number  of  cubic  centimeters  used 
will  always  be  the  per  cent,  of  S  in  hundredths.  For  example,  suppose 
the  test  has  shown  10.3cc  of  iodine  to  be  equivalent  to  .005  of  sulphur 
instead  of  lOcc,  Ice  of  this  iodine  will  be  equivalent  to  .0004854  grms.  of 
sulphur  and  one  litre  to  0.4854  grms. 

Now,  if  4.854  grms.  be  taken  for  the  analysis,  each  cc  of  iodine  so- 
lution will  be  equivalent  to  0.01  per  cent,  of  S. 

This  method  of  applying  the  factors  of  volumetric  solutions  to  the 
amount  weighed  out  may  be  applied  to  any  volumetric  process,  as  for 
phosphorus,  iron,  or  manganese. 

Additional  Notes  on  the  Process.— It  is  essential  that  everything  be 
carried  out  promptly.  The  NaHO  solution  must  not  be  allowed  to  stand 
before  titration,  or  the  sulphide  will  oxidize. 

The  diluted  solution,  after  the  addition  of  HC1,  will  change  very 
rapidly  if  not  titrated  at  once. 

It  is  desirable  that  the  NaHO  be  free  from  iron,  which  will  form 
ferric  chloride  and  destroy  the  HaS.  Prepare  the  alkali  solution,  let  it 
stand  till  any  precipitate  of  Fe2O3  settles,  and  use  the  clear  solution. 

By  adding  a  drop  of  phenolpthaline  solution  to  the  dilute  soda  so- 
lution, the  neutralization  by  HC1  is  made  easy  as  the  red  color  of  this 
indicator  is  at  once  discharged  when  the  HC1  is  in  excess. 

Modifications  of  the  Iodine  Method.  —  The  most  important  consists 
in  substituting  an  ammoniacal  solution  of  a  cadmium  salt  for  the  NaHO. 
The  sulphur  is  absorbed  and  precipitated  as  CdS.  This  is  filtered  from 
the  excess  of  alkaline  liquid,  filter  and  all  are  put  in  a  large  amount  of 
water,  HC1  added,  which  dissolves  the  CdS  and  liberates  H2S,  this  is 
then  titrated  as  usual.  This  method  avoids  the  titration  in  the  presence 
of  any  hydrocarbons  absorbed  by  the  alkali  in  the  ordinary  process. 
These,  some  claim,  may  absorb  iodine. 

See  Blair,  Chem.  Anal.  Iron  and  Steel,  p.  71. 

The  cadmium  solution  may  be  made  as  follows : 
75cc  H2O— 75cc  NH4HO  3  grms.  CdCl2. 

For  use  add  5cc  of  this  to  95cc  of  water  (formula  communicated  by 
Mr  Davis). 

THE  DETERMINATION  OF  CARBON  IN  PIG 
IRON  AND   STEEI*. 

The  carbon  in  gray  pig  iron  occurs  principally  as  u  free  carbon  "  or 
graphite.  A  smaller  portion  is  combined  with  the  iron  as  u  carbide," 
constituting  the  so-called  "  combined  carbon." 

In  white  iron  and  "  chilled  iron,"  as  also  in  steel,  especially  mild  or 
low  carbon  steel,  most  of  the  carbon  is  combined. 


60  Notes  on  Metallurgical  Analysis. 

When  these  metals  are  dissolved  in  hot  HC1  the  graphite  is  left  as 
a  black,  scaly  residue,  while  the  combined  carbon  mostly  passes  off  with 
the  hydrogen  as  hydro-carbon  gases. 

Carbon  is  always  determined  by  oxidizing  it  to  CO2,  then  absorbing 
the  gas  in  a  weighed  amount  of  KHO,  or  other  absorbent.  The  gas  may 
also  be  determined  by  measuring  its  volume  by  the  processes  of  gas 
analysis.  In  the  hands  of  very  skillful  operators  this  would  seem  a 
feasible  method. 

Jour.  Soc.  Chem.  Ind.,  9,  p.  768;  10,  p.  658;  also  p.  1033. 

The  carbon  is  converted  to  CO2  when  iron  is  completely  burned  in 
oxygen  gas.  Unfortunately  this  simple  method  cannot  be  used  in  most 
cases,  because  when  iron  fragments  are  heated  in  oxygen  they  become 
coated  with  a  layer  of  oxide,  which  protects  the  interior  from  further 
action,  and  so  a  portion  of  the  carbon  remains  unburned,  even  hours  of 
heating  failing  to  reach  it  all. 

Hence,  this  method  is  only  applicable  where  the  iron  can  be  re- 
duced to  a  very  fine  powder,  a  condition  usually  practically  unattainable. 

The  first  step  in  the  carbon  determination  is  to  liberate  it  from  the 
iron,  by  dissolving  the  latter  in  some  solvent,  which  will  leave  all  the 
carbon  unattacked  as  a  residue. 

The  carbon  thus  liberated  is  filtered  out  on  to  ignited  asbestos  and 
then  burned  to  CO2  in  oxygen  or  by  chromic  acid  and  sulphuric  acid. 

Several  methods  of  solution  have  been  used.  The  essential  condi- 
tion is  that  no  hydrogen  gas  be  liberated,  as  it  will  carry  off  carbon,  and 
no  strong  oxidizing  agent  be  present,  or  it  will  oxidize  carbon. 

The  most  rapid  solvent  for  iron  which  fulfills  these  conditions  is  a 
saturated  solution  of  ammonium  or  potassium  cupric  chloride. 

The  reaction  by  which  the  iron  is  dissolved  is 

Fe  -f  2  (NHJ  Cu  C13  —  Fe  C12  +  Cu2  C12  +  2NH4  Cl. 

The  NH4  Cl  serves  to  hold  the  cuprous  salt  in  solution  and  greatly 
hastens  the  action. 

The  solution  has  a  tendency  to  dissolve  organic  matter,  which  is 
liable  to  be  precipitated  subsequently  with  the  carbon  in  the  steel.  This 
is  especially  true  of  the  ammonium  salt.  It  is  very  difficult  to  obtain 
the  ammonium  compound  free  from  organic  matter,  derived  from  the 
ammonium  salts  used  in  its  manufacture.  The  salt  should  be  thor- 
oughly purified  by  re-crystallization. 

A  large  excess  of  the  solution  is  required  to  prevent  the  separation 
of  metallic  copper  with  the  carbon. 

The  carbon  residue  retains  chlorides  very  difficult  to  wash  out,  and 
which  cause  trouble  in  the  subsequent  combustion.  This  is  especially 
true  if  any  metallic  copper  is  left  mixed  with  the  carbon,  as  it  forms 
basic  subchlorides.  The  spongy  carbon  is  best  freed  from  these  chlorides 
by  treatment  with  HC1  and  then  washing. 


Notes  on  Metaliurgicar^&Q^  61 


For  very  important  papers  on  the  carbon  determination  consult — 

Langley  Trans.  Am.  Inst.  Min.  Engs.,  vol.  XIX,  p.  614. 
Shimer  Jour.  An.  and  App.  Chem.,  vol.  V,  p.  129. 
Blair,  Jour.  An.  and  App.  Chem.,  vol.  V,  p.  122. 

Process  —  Solution  of  the  Metal  and  Separation  of  the 
Carbon. — Prepare  a  solution  of  the  double  chloride  of  copper 
and  ammonium  or  potassium.  Use  the  purest  crystallized 
salt  obtainable.  Dissolve  one  part  in  three  parts  of  pure 
water,  free  from  grease  or  organic  matter.  Then  add  NH4 
HO  drop  by  drop  until  a  slight  permanent  precipitate  forms, 
let  settle,  decant  off  the  clear  solution,  and  filter  the  turbid 
portions  through  ignited  asbestos. 

The  drillings  of  metal  must  be  free  from  all  grease  or  intermixed 
particles  of  wood,  straw  or  paper.  They  may  be  separated  from  the 
latter  by  a  magnet,  from  the  former  by  washing  them  with  pure  ether 
and  drying.  Care  in  drilling  and  handling  the  sample  will  render  this 
unnecessary. 

Weigh  out  two  grms.  of  pig  iron,  three  grms.  of  high 
carbon  steel  or  five  grms.  of  low  carbon  steel  or  wrought 
iron.  Put  them  in  a  No.  2  or  No.  3  beaker,  and  add  at  once 
50cc  of  the  copper  solution  for  each  grm.  taken.  Stir  the 
solution  continuously  until  the  iron  is  dissolved.  The  com- 
pletion of  the  reaction  is  easily  recognized  by  the  residue 
becoming  light  and  "  flotant.''  At  first  more  or  less  copper 
will  separate,  but  stirring  and  time  will  bring  it  into  solu- 
tion. Now  add  5  to  lOcc  of  cone.  HC1,  and  when  all  the  free 
copper  is  dissolved,  filter  on  to  an  asbestos  filter.  The  asbes- 
tos must  be  thoroughly  ignited  in  air  before  using  to  remove 
any  carbonaceous  matter. 

When  the  liquid  has  run  through,  wash  out  the  beaker 
and  transfer  all  adhering  carbon  to  the  filter,  using  HC1  di- 
luted with  its  own  volume  of  water.  Wash  the  carbon  on  the 
filter  twice  with  the  acid,  letting  it  run  through  slowly  to 
give  it  time  to  act.  Now  wash  with  water  until  all  the  HC1 
is  removed  and  the  filtrate  does  not  react  with  Ag  NO3. 

The  filtrate  will  be  dark  colored  at  first,  but  when  diluted 
with  the  HC1  and  water  will  become  light,  and  then  must  be 
carefully  examined  to  see  that  no  particles  of  carbon  have 
run  through  the  filter. 


62  Notes  on  Metallurgical  Analysis. 

In  the  above  process  double  chloride  of  copper  and  potassium  may 
be  used  in  place  of  the  ammonium  compound.  It  is  said  to  be  more 
easily  obtained  pure. 

Some  chemists  add  a  little  HC1  to  the  copper  solution  before  adding 
it  to  the  metal. 

Determination  of  the  Carbon  by  Oxidation  with  Chromic 
Acid  and  Weighing  the  CO2  Produced. 

Carbon  in  any  form  is  rapidly  and  completely  converted  to  CO2 
when  heated  with  chromic  acid  and  an  excess  of  sulphuric  acid,  chro- 
mium sulphate  being  formed. 

The  important  condition  is  the  strength  of  the  H2SO4.  If  too 
weak,  the  boiling  point  is  too  low  and  carbon  will  escape  oxidation.  If 
the  acid  is  too  strong,  when  the  mixture  is  boiled,  oxygen  will  be  given 
off  and  white  fumes  of  H2SO4  will  form,  which  are  difficult  to  arrest  in 
the  purifying  apparatus,  and  are  liable  to  cause  high  results. 

The  proper  strength  for  the  acid  in  the  reaction  is  between  1.4  and 
1.6  sp.  gr.  This  corresponds  to  from  50  to  70  per  cent,  of  H2SO4  in  the 
mixture. 

If  the  carbon  retains  chlorine  or  chlorides,  chlorochromic  acid  gas 
may  form,  escape  with  the  CO2  and  be  absorbed  by  the  KHO,  causing 
false  results  unless  special  means  be  taken  for  absorbing  it. 

The  H2SO4  used  must  be  purified  from  all  organic  matter. 

Arrangement  of  the  Apparatus. —  1.  An  Erlenmeyer 
flask  of  about  250cc  capacity  fitted  with  a  2-hole  rubber 
cork.  Into  this  is  inserted  a  bulb  funnel  tube  having  a  glass 
stopcock,  and  a  delivery  tube  for  the  gas. 

This  latter  should  be  of  rather  large  diameter  and  so  inclined  that 
everything  condensing  in  it  shall  run  back  into  the  flask.  It  is  a  good 
plan  to  have  it  cooled  by  a  "  water  jacket"  consisting  of  a  larger  tube 
surrounding  it,  the  space  between  the  two  being  filled  with  water. 

2.  Fit  a  small  "  guard  tube  ''  filled  with  "  soda  lime  " 
into  the  top  of  the  funnel  tube. 

This  is  easily  made  of  a  test  tube  drawn  out  into  a  narrow  neck 
which  is  put  through  a  small  rubber  cork.  Put  a  layer  of  cotton  on  the 
bottom  to  prevent  any  soda  lime  dropping  through. 

This  serves  to  purify  the  air  drawn  into  the  flask  from  all  CO2.  It 
must  be  arranged  so  as  to  \  e  easily  removed  or  connected. 

3.  Connect  the  delivery  tube  with  the  following  purify- 
ing and  absorbing  apparatus  (or  "train")  arranged  in  the 
order  given. 

A.     A  small  (50  to  75cc  capacity)  bottle  containing  u  pyro 


Notes  on  Metallurgical  Analysis.  63 

solution,"  made  by  mixing  0.2  grm.  pyrogallic  acid  with  5 
grms.  neutral  potassium  oxalate,  adding  water  enough  to 
make  20cc  and  then  2  drops  of  H2SO4  which  must  make  the 
solution  distinctly  acid. 

This  will  absorb  all  free  chlorine  and  chlorochromic  acid.  Its  use  is 
due  to  Langley. 

B.  A  similar  bottle  containing  about  20cc  of  an  acid 
solution  of  silver  sulphate. 

This  serves  to  absorb  any  HC1  vapors.  It  must  follow  "A"  as  the 
action  of  the  pyro  is  to  form  HC1  from  the  oxides  of  chlorine. 

The  silver  sulphate  is  easily  made  by  dissolving  about  0.5  grm.  of 
AgNO3  in  a  little  water  adding  Ice  cone.  H2SO4,  evaporating  till  the 
HNO3  is  all  expelled  cooling  and  diluting  largely  with  water.  Ag2SO4 
is  only  sparingly  soluble. 

C.  A  bottle  containing  20  or  30cc  of  cone. pure  H2SO4. 
This  takes  out  all  the  water  vapor  from  the  gas. 

D.  A   U-tube   containing  granular  CaCl2.     Fill  about 
an  inch  of  the  tube,  on  the  side  next  to  the  H2SO4  with  cot- 
ton and  moisten  the  top  of  this  with  a  drop  of  water.    (Blair.) 

The  object  of  this  CaCl2  is  to  absorb  H2O  and  to  bring  the  gas 
stream  entering  the  absorption  apparatus  (  E  and  F  )  into  the  same  con- 
dition as  to  moisture,  in  which  it  leaves  it.  H2SO4  will  dry  air  more 
completely  than  CaCl2,  hence  if  the  gas  entered  through  H2SO4  and 
left  through  CaCl2  it  would  carry  out  more  moisture  from  the  KHO 
bulbs  than  it  brought  in  and  so  result  in  loss  of  weight.  The  introduc- 
tion of  the  moist  cotton  is  only  necessary  when  the  CaCl2  is  very  dry, 
after  it  has  absorbed  a  little  water,  it  will  itself  give  up  enough  to  the 
air  to  serve  the  purpose. 

Dried  CaCl2  and  not  the  fused  salt  should  be  used.  This  latter  is 
usually  alkaline  from  free  CaO  and  will  absorb  some  CO2. 

B.  Liebig's  potash  bulbs  containing  a  clear  solution  of 
KHO  of  about  1.27  sp.  gr.,  (about  30  per  cent). 

This  absorbs  the  CO2,  but  not  completely  unless  the  gas  stream  is 
slow.  The  solution  loses  water  vapor  to  a  small  extent.  If  made 
stronger  than  directed  it  deposits  K2CO3  and  may  clog  up  the  tube. 

F.  A  small  U-tube,  the  limb  next  the  potash  bulbs 
filled  with  granular  soda  lime  which  should  not  be  too  dry. 
The  other  limb  is  filled  with  granular  CaCl2. 

This  tube  serves  to  catch  any  trace  of  CO2  escaping  the  bulbs,  and 
also  to  retain  all  moisture.  Soda  lime  is  a  more  rapid  and  complete 


64  Notes  on  Metallurgical  Analysis. 

absorbent  for  CO2  than  the  bulbs,  but  it  is  rapidly  exhausted,  hence  by 
letting  the  bulbs  do  most  of  the  work  and  only  using  the  soda  lime  for 
the  finish  it  lasts  for  several  operations  and  retains  every  trace  of  the 
CO2.  The  potash  bulbs  and  the  soda  lime  —  CaCl2  tube  are  the  parts 
of  the  train  to  be  weighed. 

G.  A  U-tube  similar  to  the  the  last,  but  larger,  having 
the  limb  next  to  F  rilled  with  CaCl2,  and  the  other  with 
granular  soda  lime. 

This  serves  as  a  guard  tube  to  prevent  moisture  or  CO2  working 
back  into  the  absorption  apparatus  from  the  aspirator.  It  can  be  used 
almost  indefinitely. 

H.  An  aspirator  for  sucking  air  slowly  through  the 
apparatus. 

This  must  be  easily  attached  and  detached.  It  can  be  made  from 
a  five-pint  acid  bottle  by  boring  a  hole  near  the  bottom  with  a  pointed 
file  dipped  in  turpentine,  fitting  a  glass  tube  in  this  by  a  rubber  ring 
and  then  attaching  to  this  a  rubber  tube  and  pinch-cock. 

Notes  on  the  above  Apparatus. —  It  is  essential  that  none  of  the 
chromic  acid  solution  come  in  contact  with  the  rubber  corks  or  connec- 
tions, as  it  would  of  course  form  CO2.  For  similar  reasons  it  is  neces- 
sary that  the  glass  stopcock  in  the  funnel  tube  be  free  from  grease  of 
any  sort. 

A  flask  provided  with  a  ground  glass  cap,  into  which  the  tubes  are 
fused,  is  a  very  good  substitute  for  the  corked  flask  described.  It  is,  of 
course,  more  expensive. 

Liquids  always  absorb  some  little  CO2,  hence  the  volume  of  all 
absorbing  liquids  used  in  purifying  must  be  small.  This  CO2  is,  how- 
ever, given  up  again  to  a  current  of  air  passed  through  them  for  some 
time. 

The  details  of  the  mechanical  arrangement  of  the  train  will  vary 
with  the  operator.  For  drawings  showing  convenient  plans  see 

Jour.  An.  and  App.  Chem.,  vol.  V.,  page  336. 

Setting  Up  and  Testing  the  Apparatus. — The  connections 
are  made  by  glass  tubes  united  by  short  rubber  tubes. 
These  must  be  carefully  tied  with  thread  or  wire,  as  it 
is  essential  that  the  whole  apparatus  be  air  tight.  Rubber 
corks  are,  of  course,  the  best,  but  good  ordinary  corks 
can  be  used  if  rolled  soft  and  carefully  bored  and  fitted. 
Sealing  wax  is  often  recommended,  to  make  joints  tight, 
but  it  is  a  bad  thing  to  use,  as  it  will  crack  and  leak  unex- 
pectedly. The  potash  bulbs  and  U-tube  must  be  u  capped '' 


Notes  on  Metallurgical  Analysis.  65 

with  short  rubber  tubes  closed  with  bits  of  glass  rod. 
These  must  always  be  removed  for  a  moment  and  then 
replaced  just  before  weighing,  that  the  air  pressure  inside 
and  outside  may  equalize  itself. 

It  is  necessary  to  first  pass  some  CO2  through  the  appa- 
ratus in  order  to  saturate  any  alkaline  material  present  in 
the  CaCl2,  etc.  When  this  is  done  of  course  the  weighed 
part  of  the  train  is  omitted.  Connect  up  the  train,  leaving 
out  the  parts  E,  F  and  G.  Put  a  little  marble  in  the  flask, 
add  a  little  dilute  H2SO4  so  as  to  generate  a  slow  stream 
of  CO2.  Let  this  run  through  this  portion  of  the  train  for 
about  thirty  minutes.  Disconnect  and  wash  out  the  flask, 
replace  it,  and  now  aspirate  air  alone  until  six  or  eight  litres 
have  been  slowly  drawn  through. 

Now,  connect  up  the  whole  apparatus  and  attach  the 
aspirator.  Close  the  stopcock  in  the  funnel  tube  of  the 
flask  and  see  if  all  connections  are  tight.  This  is  proved 
by  the  water  ceasing  to  run  from  the  aspirator.  Cautiously 
let  in  air  by  opening  the  stopcock.  Attach  the  soda  lime 
guard-tube  to  the  funnel  tube  and  aspirate  one  or  two 
litres  of  air  carefully  (not  over  one  or  two  bubbles  a 
second).  Disconnect  the  bulbs  and  the  U-tube,  cap  them, 
and  wipe  them  carefully.  Set  them  in  or  near  the  bal- 
ance case  until  they  attain  its  temperature  (ten  or  twenty 
minutes).  Uncap  them  a  moment,  replace  the  caps  and 
then  carefully  weigh  them.  Replace  the  apparatus  and  as- 
pirate three  or  four  litres  of  air  more  and  reweigh  them  as 
before.  The  KHO  bulbs  will  lose  (due  to  moisture)  and  the 
U-tube  will  gain  weight.  The  loss  in  one  must  equal  the 
gain  in  the  other.  The  total  weight  of  the  absorption  appa- 
ratus must  not  change  more  than  one-half  millegramme. 

The  Treatment  of  the  Carbon  in  the  Residue  from  the 
Iron. — Transfer  this  to  the  flask,  using  a  little  water  to  wash 
out  the  filter  tube.  The  total  amount  of  liquid  in  the  flask 
must  not  exceed  30cc.  Now  dissolve  four  grms.  of  chromic 
acid  in  4cc  of  water,  and  pour  it  into  the  flask  through  the 


66  Notes  on  Metallurgical  Analysis. 

funnel  tube.  Wash  out  the  tube  with  2  or  3cc  of  water. 
Now  estimate  the  amount  of  liquid  in  the  flask  by  compar- 
ison with  a  similar  one,  and  put  in  the  bulb  of  the  funnel  a 
quantity  of  pure  concentrated  H2SO4,  equal  to  about  twice 
the  volume  of  the  liquid  in  the  flask. 

This  acid  should  be  previously  purified  by  adding  to  a  quantity  of 
it  a  little  chromic  acid,  heating  it  to  200°C  and  letting  it  cool.  This  will 
destroy  any  trace  of  organic  matter  it  may  contain. 

Allow  the  acid  to  run  into  the  flask  gradually  and  care- 
fully to  avoid  too  violent  action.  Shake  the  flask  up  care- 
fully to  mix  the  solution.  The  evolution  of  CO2  will  begin  at 
once.  Finally  heat  with  a  lamp  until  the  liquid  begins  to 
boil.  Continue  this  till  no  more  bubbles  come  over  through  the 
bottles  in  the  train.  A  sharp  rattling  sound  usually  marks 
this  point.  The  time  of  boiling  should  not  exceed  one  or 
two  minutes.  Now  withdraw  the  lamp  and  immediately 
open  the  stopcock  of  the  funnel  tube  to  admit  air  and  pre- 
vent back  suction.  Connect  the  funnel  tube  with  the  soda 
lime  guard  tube,  and  let  the  apparatus  cool  a  few  minutes. 
Then  aspirate  carefully  four  or  five  litres  of  air  (or  more  if 
the  apparatus  is  large).  Detach  the  absorption  apparatus 
and  weigh  as  before.  The  total  gain  in  weight  will  be  the 
amount  of  CO2,  and  this  multiplied  by  0.2727  gives  the 
amount  of  carbon. 

The  greatest  care  and  "handiness"  are  necessary,  but  with  skill  du- 
plicates should  agree  within  0.01  per  cent. 

Note  1. — The  "  weighing  out "  of  pig  iron  for  carbon  is  a  matter  of 
great  difficulty,  as  the  fine,  dusty  portion  is  usually  higher  in  carbon 
than  the  lumps.  A  method  proposed  by  Dr.  Shimer  is  to  moisten  the 
drillings  with  alcohol,  so  that  the  fine  may  stick  to  the  coarse.  Then 
take  a  portion  of  approximately  the  right  amount,  put  it  on  a  weighed 
watch  glass,  dry  it  carefully  and  re  weigh,  using  this  amount  for  the  de- 
termination. 

Note  2. — This  method  of  combustion  with  chromic  acid,  while  less 
elegant  than  the  combustion  by  oxygen  gas  in  a  glass,  porcelain  or  plat- 
inum tube  is  accurate,  and  demands  much  less  expensive  apparatus. 

For  the  combustion  in  oxygen  see— 

Blair  Chem.  Anal.  Iron  and  Steel,  p.  125,  et  seq  ;  also  Langley  paper  Trans.  Am.  Inst. 
Min.  Engs.,  vol.  XIX,  p.  614. 


Notes  on  Metallurgical  Analysis.  67 

THE  DETERMINATION  OF  CARBON  IN  STEEL  BY  COLOR. 

This  method  is  in  universal  use  in  steel  works.  It  depends  upon 
the  fact  that  when  steel  is  dissolved  in  dilute  HNO3  there  separates  a 
brown  compound  containing  the  carbon,  which  on  boiling  goes  into 
solution  giving  a  color  which  is  deeper,  as  the  per  cent,  of  carbon  is 
higher.  Pure  iron  dissolves  in  HNO3  giving  a  nearly  colorless  solution, 
from  which  moderate  dilution  removes  every  trace  of  color. 

The  color  produced  by  the  carbonaceous  matter  is  rapidly  altered 
by  light.  Its  depth  depends  somewhat  on  the  mode  of  solution,  the 
concentration  of  the  acid  and  the  kind  of  steel ;  hence  the  process  must 
be  conducted  strictly  according  to  rule  to  get  good  results. 

There  is  required,  first,  a  standard  steel,  which  must  be  of  exactly 
the  same  kind  as  that  to  be  tested,  and  also  be  similar  in  its  composition 
and  of  approximately  the  same  carbon  percentage.  The  carbon  in  this 
must  have  been  accurately  determined  gravi  metrically;  second,  nitric  acid 
of  1.2  sp.  gr.  perfectly  free  from  chlorine,  as  the  least  trace  will  seriously 
alter  the  color  of  the  iron  solution,  making  it  more  yellow.  The  above 
strength  corresponds  to  1  of  cone,  acid  to  1  of  water ;  third,  c  mparison 
tubes  of  clear  white  glass,  graduated  in  TVcc,  and  of  exactly  equal 
diameter. 

For  comparing  the  colors  a  blackened  box  with  a  ground  glass  win- 
dow in  the  end  is  convenient. 

See  Blair,  Chem.  An.  Iron  and  Steel,  Second  Edition,  p.  167. 

Process. — Weigh  0.2  grm.  of  the  steel  and  of  the 
standard,  each  into  a  6-in.  test  tube.  Add  to  each  tube  a 
measured  volume  of  cold  HNO3  1.2  sp.  gr.,  using  the  follow- 
ing amounts  :  For  steels  with  not  over  T2^  per  cent,  carbon, 
4cc;  from  -fa  to  f5¥  per  cent.,  6cc;  from  -f$  to  1  per  cent., 
8cc;  and  over  1  percent.,  IGcc. 

Stand  the  tubes  in  cold  water  till  violent  action  ceases. 
Then  set  them  in  a  water  bath  kept  boiling  and  boil  until 
the  solution  is  perfectly  clear  and  no  more  bubbles  of  fine 
gas  appear.  Keep  the  mouths  of  the  test  tubes  closed  loosely 
by  little  glass  bulbs  or  balls  to  prevent  drying  of  the  iron 
salts  on  the  sides  of  the  tubes.  The  time  required  will  be 
15  to  30  minutes,  according  to  the  carbon  contents  of  the 
steel.  Now  cool  the  tubes  in  water.  Add  an  equal  volume 
of  water  to  each  and  pour  into  the  comparison  tubes.  Dilute 
carefully  until  the  colors  match.  The  percentages  of  the 
carbon  will  be  to  each  other  as  the  volumes  in  the  tubes. 


68  Notes  on  Metallurgical  Analysis. 

Where  a  number  of  steels  are  to  be  tested  at  once  it  is  convenient 
to  dilute  the  standard  until  each  cc  represents  some  definite  percentage 
of  carbon,  and  then  match  it  with  the  others,  so  that  the  readings  in  cc's 
can  be  at  once  converted  to  per  cents.  For  example,  if  the  standard 
contained  0.38%  C,  dilute  it  to  19cc,  then  if  a  comparison  showed  the 
unknown  steel  to  read  16cc  it  would  obviously  contain  0.32^  carbon. 

Note. —  If  the  steel  contains  much  sulphur  the  solution  will  be 
slightly  turbid  from  free  S.  Comparison  is  difficult  in  this  case. 

Many  modifications  of  this  process  are  proposed.  First,  by  the  use 
of  permanent  standard  colors  to  avoid  dissolving  a  standard  steel  every 
time.  Both  organic  and  inorganic  colors  (chlorides  of  Fe,  Cu  and  Co), 
are  used,  but  the  safest  way  is  to  do  as  above  described. 

For  these  methods  see  Am.  Inst.  Min.  Engrs.,  vol.  XVI,  p   111,  also  vol.  I,  p.  240. 

For  very  low  carbon  steels  the  color  is  very  faint  and  uncertain.  In 
such  cases  an  alkaline  method  has  been  used. 

Stead,  Jour.  Iron  and  Steel  Inst.,  1883,  No.  1,  p.  213,  or  Blair,  Chem.  Anal.  Iron  and  Steel, 
Second  Edition,  p.  170. 

DETERMINATION   OF   "GRAPHITE"    OR   UNCOMBINED   CARBON 

IN   PIG   IRON. 

Treat  2  grms.  in  a  beaker  with  50cc  of  HC1,  sp.  gr.  1.12. 
Cover  and  boil  briskly  for  30  minutes.  Dilute,  filter  on  an 
asbestos  filter  and  wash  first  with  hot  water,  then  with  a  solu- 
tion of  caustic  soda,  then  with  water,  then  with  alcohol,  then 
with  ether  and  finally  with  water  first  cold  then  hot,  till  every 
trace  of  ether  is  extracted.  Now  transfer  to  the  carbon  ap- 
paratus and  treat  with  chromic  acid  and  sulphuric  acid  as  in 
the  determination  of  total  carbon. 

Drown,  Trans.  Am.  Inst.  Min.  Engrs.,  vol.  Ill,  p.  41. 

This  complicated  washing  is  required  to  remove  solid  and  liquid 
hydrocarbons  which  are  liable  to  form  and  are  insoluble  in  water  alone. 

DETERMINATION  OF  TITANIUM  IN  IRON  ORES. 

Titanium  usually  occurs  in  iron  ores  as  menaccanite.  It  is  seldom 
found  except  in  magnetites. 

If  titaniferous  iron  ores  are  boiled  with  concentrated  HC1  most  of 
the  TiO2  goes  into  solution,  provided  the  material  is  reduced  to  an  exces- 
sively fine  powder. 

Rutile,  ignited  TiO2  and  other  compounds  of  titanium,  which  are 
not  attacked  by  HC1,  can  be  dissolved  after  fusion  with  acid  potassium 
sulphate  (KHSO4).  The  fusion  is  slowly  but  completely  dissolved  by 


Notes  on  Metallurgical  Analysis.  69 

cold  water.  Titanic  acid  and  iron,  with  other  bases  going  into  solution 
as  sulphates,  while  only  silica  is  left  as  a  residue.  Should  phosphoric 
acid  be  present,  some  TiO2  is  liable  to  remain  as  phosphate  with  the  SiO2 
however. 

When  ores  or  other  compounds  containing  titanium  are  fused  with 
a  large  excess  of  dry  sodium  carbonate,  they  are  completely  decom- 
posed, provided  they  are  very  finely  pulverized.  When  the  "  melt"  is 
boiled  with  water  till  thoroughly  disintegrated,  sodium  phosphate,  so- 
dium aluminate  and  sodium  silicate  go  into  solution,  while  sodium  ti- 
tauate  remain  entirely  insoluble  with  the  oxide  of  iron  and  other  bases. 
The  separation  in  the  case  of  the  phosphates  is  complete,  in  the  case  of 
silicate  and  aluminate  partial. 

The  residue  of  titanate,  etc.,  is  now  soluble  in  HC1  or  even  more 
readily  in  hot  H2SO4.  The  solution  may  be  freed  from  silica  by  evap- 
oration with  H2SO4  till  HC1  is  expelled  and  the  silica  dehydrated.  This 
will  also  dissolve  any  TiO2  the  HC1  does  not  attack.  On  dilution  with 
water  the  TiO2  and  the  bases  will  all  go  into  solution  as  sulphates,  while 
the  SiO2  is  left  insoluble  and  free  from  TiO2. 

TiO2  is  precipitated  from  slightly  acid  solutions  on  boiling  —  as  a 
hydrate.  That  the  precipitation  may  be  complete,  it  is  necessary  that 
not  more  than  one-half  per  cent,  of  free  acid  be  present,  that  the  solu- 
tion be  dilute,  the  boiling  prolonged  and  that  phosphoric  acid  be  absent 
or  present  only  in  traces.  Ferric  oxide,  alumina  and  phosphoric  acid,  if 
present,  invariably  come  down  with  the  TiO2  in  considerable  amount. 

The  precipitate  tends  to  adhere  to  the  glass,  is  fine  and  difficult  to 
filter  and  wash. 

The  precipitated  titanic  hydrate  is  soluble  with  difficulty  in  min- 
eral acids,  and  is  insoluble  in  acetic  acid. 

Solutions  containing  TiO2  are  completely  precipitated  by  ammonia. 
TiO2  is  also  precipitated  on  boiling  completely  and  promptly  from  solu- 
tions containing  sodium  acetate  and  a  large  excess  of  acetic  acid  (15  to 
20  per  cent.),  provided  ferric  salts  are  not  present.  If  phosphoric  acid 
is  present  it  will  come  down  with  the  TiO2.  As  alumina  is  not  precip- 
itated under  these  conditions,  the  TiO2  will  be  nearly  free  from  it,  and 
a  repetition  of  the  process  will  give  a  good  separation. 

See  Gooch.  Chem.  News,  vol,  LI  I,  p.  55. 

The  best  solvent  for  hydrated  TiO2  is  a  mixture  of  eight  parts  of  cone, 
H2SO4  and  three  parts  of  water,  heated  to  its  boiling  point. 

If  this  solution  is  concentrated  by  boiling  until  the  water  is  all  ex- 
pelled, the  TiO2  will  separate  again  in  a  form  which  cannot  be  redis- 
solved ;  hence,  in  the  process  which  follows  avoid  too  high  heating  of 
the  sulphuric  acid  solutions. 

Process  for  Iron  Ores. —  Take  one  or  two  grins,  (the  ore 
must  be  ground  to  an  impalpable  powder),  put  it  into  a 


70  Notes  on  Metallurgical  Analysis. 

small  covered  beaker,  add  30cc  of  concentrated  HC1,  and 
boil  gently  till  the  iron  appears  dissolved.  Now  add  lOcc  to 
15cc  of  dilute  H2SO4  (1  to  4  of  water),  boil  down  till  the  HC1  is 
all  expelled  and  fumes  of  H2SO4  just  begin  to  appear,  but 
avoid  over-heating.  Cool;  add  25cc  of  H2O  and  boil  till -all 
iron  salts  are  dissolved ;  filter  and  wash.  Dry  and  save  the 
residue  to  be  examined  for  TiO2.  It  is  usually  free  from  it, 
but  may  contain  a  considerable  amount. 

Dilute  the  filtrate  to  250cc  or  300cc.  Add  NH4HO  care- 
fully until  the  precipitate  formed  at  first  only  dissolves 
slowly  on  stirring.  Now  warm  the  solution  and  add  slowly, 
a  little  at  a  time,  a  solution  of  sodium  sulphite,  1  in  5,  made 
distinctly  acid  by  adding  a  little  H2SO4.  The  deep  color 
produced  by  each  addition  will  rapidly  disappear  as  the  iron 
is  reduced. 

Should  the  liquid  grow  turbid  and  a  precipitate  form,  add 
a  few  drops  of  HC1  to  clear  it,  and  continue  with  the  sulphite 
solution,  giving  time  for  the  reaction.  The  solution  should 
not  be  heated  to  boiling  or  TiO2  will  separate  as  a  white, 
milky  precipitate,  not  redissolving  by  the  addition  of  a  few 
drops  of  HC1.  This  will  do  no  harm  except  as  it  makes  the 
reduction  difficult  to  follow.  Add  in  this  way  40cc  to  60cc 
of  the  sulphite  solution.  The  liquid  should  now  be  colorless 
and  smell  strongly  of  SO2.  If  still  colored  from  ferric  iron  a 
few  moments'  heating  will  reduce  it.  Now  add  50cc  to  60cc 
of  acetic  acid,  and  then  20  grms.  of  sodic  acetate,  and  boil 
hard  for  three  minutes.  The  TiO2  will  separate  as  a  floccu- 
lent  precipitate.  Let  this  settle,  filter,  and  wash  with  hot 
water.  Call  this  precipitate  A  ;  it  contains  all  the  TiO2  but 
is  impure. 

Treatment  of  the  Residue. —  Put  filter  and  residue  into  a 
platinum  crucible  and  ignite  until  all  carbon  is  burned  off. 
Now  add  ten  times  its  weight  of  dry  Na2CO3  and  fuse  over  a 
blast  lamp  until  thoroughly  decomposed.  Cool,  add  water  and 
boil  until  all  is  thoroughly  disintegrated  and  the  residue  is 
flocculent.  Filter  and  wash  with  hot  water.  Wash  the  resi- 


Notes  on  Metallurgical  Analysis.  71 

due  from  the  filter  into  a  beaker  with  a  little  water.  Let 
it  settle  and  decant  the  water  off  through  the  filter  again. 
Dissolve  the  little  adhering  residue  from  the  filter  with  a  few 
drops  of  HC1,  running  it  through  into  the  rest.  Add  a  little 
HC1  to  the  beaker  and  residue,  then  lOcc  of  dilute  H2SO4 
(1  to  4)  and  boil ;  all  will  dissolve.  Evaporate  until  all  HC1 
is  expelled,  just  as  with  the  original  solution.  Add  25cc 
H2O,  boil  and  filter  from  the  SiO2,  which  will  be  free  from 
TiO2.  Now  dilute  to  150cc,  add  NH4HO  till  a  slight  precipi- 
tate forms;  redissolve  this  with  a  little  HC1,  and  add  lOcc  of 
the  sulphite  solution.  If  a  precipitate  now  forms,  add  HC1 
till  it  just  dissolves.  Now  heat  gradually;  as  soon  as  the 
solution  is  colorless  add  30cc  of  acetic  acid  and  10  grins,  of 
sodium  acetate.  Boil  three  minutes.  If  any  TiO2  separates, 
filter  it  off  and  wash  as  before.  Call  this  Precipitate  B. 

Treatment  of  the  Impure  Precipitate. —  Put  Precipitates 
A  and  B  into  a  platinum  crucible.  Burn  off  the  filter  papers 
completely,  and  weigh  the  impure  TiO2.  Add  ten  times  this 
weight  of  dry  Na2CO3  and  fuse  thoroughly.  Boil  out  the 
fusion  with  water  till  completely  disintegrated ;  filter  and 
wash.  Now  wash  the  residue  off  the  filter  into  a  beaker ;  let 
the  liquid  settle  and  decant  the  clear  liquid  back  through  the 
filter  (the  object  of  this  is  to  get  the  residue  into  the  beaker, 
yet  have  very  little  water  present). 

Treat  the  filter  paper  with  a  little  cone.  HC1,  letting  it 
run  through  into  the  residue  in  the  beaker  (this  dissolves 
most  all  the  TiO2  adhering  to  the  paper).  Finally  burn  the 
paper  at  as  low  a  heat  as  possible  and  add  the  ash  (still  re- 
taining a  trace  of  TiO2)  to  the  beaker.  Dissolve  the  con- 
tents of  the  beaker  in  cone.  HC1,  then  add  lOcc  or  15cc  of 
dilute  H2SO4  and  evaporate  as  before.  Dilute  with  25cc  of 
water,  boil,  filter  and  wash.  Dilute  the  solution  to  250cc 
and  precipitate  the  TiO2  exactly  as  in  the  original  solution, 
except  that  only  20cc  of  sodium  sulphite  will  be  required  for 
the  reduction.  The  second  precipitate  of  TiO2  should  be 
white  and  pure.  It  is  dried,  ignited  intensely  and  weighed. 


72  Notes  on  Metallurgical  Analysis. 

The  ignition  should  be  repeated  and  the  precipitate  again 
weighed  until  its  weight  is  constant.  The  TiO2  must  be 
light  colored. 

The  use  of  H2SO4  in  the  above  process  serves  two  purposes.  It  sep- 
arates SiO2,  and  when  concentrated  to  the  right  strength  it  is  the  most 
powerful  solvent  for  TiO2,  dissolving  even  the  ignited  oxide  provided 
too  intense  ignition  has  been  avoided. 

PROCESS  FOK  ORES  NOT  ATTACKED  BY  HCL. 

Prepare  pure  bisulphate  of  potash  by  melting  it  in  a  platinum  dish 
or  crucible  until  all  boiling  ceases  and  it  is  in  quiet  fusion.  Cool  and 
pulverize  it  and  keep  in  a  tight  bottle. 

Mix  the  very  finely  pulverized  ore  with  15  times  its  weight  of  the 
bisulphate.  Transfer  to  a  large  platinum  crucible  and  heat  gently  till 
the  mass  melts.  Raise  the  heat  gradually  until  white  fumes  just  begin 
to  come  off  (a  low  red)  and  keep  in  quiet  fusion  20  or  30  minutes.  Avoid 
too  high  a  heat  or  the  H2SO4  will  be  driven  off  and  the  fusion  spoiled. 
Insert  a  platinum  wire  into  the  melted  mass  and  let  the  crucible  cool. 
The  fusion  will  generally  detach  itself  from  the  crucible  and  can  be 
lifted  out  by  the  wire.  Now  put  crucible  and  cover  into  a  beaker.  Add 
a  considerable  amount  of  cold  water.  Hang  the  lump  of  fused  material 
in  the  water  and  let  it  soak  out.  Everything  will  gradually  dissolve 
except  SiO2,  though  it  may  take  12  hours.  Now  filter  from  the  residue 
of  SiO2  and  proceed  as  with  the  ordinary  solution. 

The  bisulphate  fusion  may  be  made  to  dissolve  more  rapidly,  if 
after  cooling  in  the  crucible  there  is  added  a  little  cone.  H2SO4,  and  the 
whole  again  heated  till  it  melts.  On  again  cooling  the  mass  will  be 
pasty  and  dissolve  more  rapidly.  (Kennedy). 

See  Drown,  Trans.  Am.  Inst.  Min.  Engrs.,  vol.  X,  p.  137. 
Jennings,  Eng.  and  Min.  Jour.,  vol.  XLV,  p.  475. 

DETERMINATION   OF  TITANIUM   BY   COLOR. 

When  hydrogen  peroxide  (H2O2)  is  added  to  a  sulphuric  acid  solu- 
tion of  titanium,  a  yellow-  brown  coloration  is  produced,  the  intensity 
of  which  is  proportional  to  the  amount  of  TiO2.  This  is  a  very  delicate 
qualitative  test  and  has  been  made  the  basis  of  a  color  method.  The  re- 
sults are  satisfactory  for  small  percentages,  as  the  solution  of  TiO2  must 
be  very  dilute  in  order  to  conopare  colors  well.  For  details  see 

Noyes,  Jour.  An.  and  App.  Chem.,  vol.  V,  p.  39. 
Wells,  Trans.  Am.  Inst.  Min.  Engrs.,  vol.  XIV,  p.  763. 


Notes  on  Metallurgical  Analysis.  73 

THE   ANALYSIS   OF   COAL  AND    COKIC. 

The  proximate  analysis  is  that  usually  made.  This  gives  informa- 
tion as  to  the  products  of  decomposition,  but  is  of  little  value  as  deter- 
mining the  heating  power  of  a  coal. 

It  is  necessary  to  conform  strictly  to  the  method  of  analysis  that 
the  results  may  be  uniform,  as  small  variations  in  the  process  give  large 
differences  in  results. 

Coals  rapidly  lose  moisture  and  change  in  other  respects  when 
kept  in  the  powdered  condition,  hence  the  analysis  must  be  made  with- 
out delay  after  sampling. 

When  a  sample  of  coal  is  dried  at  100°  or  110°C,  it  will  lose  weight 
for  a  while  and  then  gain  from  oxidation,  hence  weighing  after  a  definite 
time  must  be  substituted  for  drying  to  a  constant  weight. 

Process  for  the  Proximate  Analysis. — Weigh  1  grm.  of 
the  coal  into  a  platinum  crucible  provided  with  a  well  fitting 
lid.  Put  it  uncovered  in  a  drying  oven  and  keep  at  105°C  for 
one  hour,  cool  and  weigh.  The  loss  in  weight  is  called 
"moisture^  and  represents  with  sufficient  exactness  the 
hygroscopic  water  in  the  coal. 

Now  cover  the  crucible  and  heat  it  over  a  Bunsen  burner 
for  three  and  one-half  minutes .  Then,  without  allowing  it  to 
cool,  substitute  a  blast  lamp  for  the  Bunsen  burner  and  heat 
three  and  one-half  minutes  longer.  Now  cool  it  rapidly  and 
weigh.  The  loss  in  weight  is  called  the  "volatile  combustible 
matter"  The  crucible  is  now  set  over  a  burner,  and  so  in- 
clined that  the  air  can  circulate  in  it,  setting  the  cover  against 
the  end  to  help  the  draught.  The  carbon  gradually  burns  out, 
and,  when  the  ash  appears  free  from  it,  the  crucible  is  cooled 
and  weighed.  It  is  again  set  over  the  lamp  and  burned  a 
few  minutes  longer  and  again  weighed.  When  the  weight 
becomes  constant,  what  is  left  is  called  "ash"  and  the  loss 
in  weight  called  "fixed  carbon."' 

Of  course  the  sum  of  the  "moisture,"  u  volatile  combustible  mat- 
ter," "  fixed  carbon  "  and  "ash  "  will  always  be  100  per  cent.  The  sum 
of  the  fixed  carbon  and  the  ash  gives  the  "  coke  "  produced. 

The  above  method  is  that  which  has  been  used  for  all  the  analyses  of 
the  Ohio  Geological  Survey  since  1880.  It  yields  fairly  constant  results. 
The  only  important  variation  in  use  consists  of  taking  the  coal  without 
previous  dnjiny,  for  the  determination  of  the  volatile  combustible  matter 


74  Notes  on  Metallurgical  Analysis. 

and  then  determining  the  moisture  in  a  separate  portion.  This  gives 
1  to  2  per  cent,  less  fixed  carbon  and  more  volatile  matter,  but  is  a  little 
more  trouble,  and  as  the  results  are  simply  those  yielded  by  a  conven- 
tional method,  the  above  is  recommended. 

See  Cairn's  Quant.  Anal.,  p.  238;  Hinrichs,  Chem.  News.,  vol.  XVIII,  p.  53. 

Determination  of  Sulphur  in  Coal — Eschka  s  Method. — 

Sulphur  exists  in  coal  in  three  forms  :  Pyrites,  "  organic  sulphur" 
and  sulphates.  By  heating  coal  with  a  mixture  of  MgO  and  Na2CO3 
and  ample  access  of  air,  all  unoxidized  sulphur  is  converted  to  sulphites 
and  sulphates  of  soda  and  magnesia.  On  boiling  out  the  burned  mass 
with  water  these,  as  well  as  any  sulphuric  acid  existing  previously  in  the 
coal  as  sulphate,  are  all  dissolved  out  as  alkaline  salts.  By  adding  bro- 
mine water  to  the  solution  all  sulphites  are  oxidized  to  sulphates,  and 
thus  the  total  sulphur  can  be  estimated  as  BaSO4  by  precipitation  with 
BaCl2, 

Preparation  of  the  Soda  Magnesia  Mixture  {Eschka  Mix- 
ture). — Take  a  good  quality  of  commercial  "light  calcined 
magnesia'1  and  purify  it  from  sulphur  as  follows:  Add 
about  two  per  cent,  of  C.  P.  sodic  carbonate,  and  then  stir  it 
tip  in  enough  boiling  water  to  make  a  thin  liquid.  Boil  the 
mixture  a  few  minutes  and  let  settle,  decant  off  the  liquid 
by  a  siphon.  Add  water  again,  stir  up,  settle,  and  again  de- 
cant. Continue  this  washing  by  decantation  until  the  liquid 
after  being  acidified  with  HC1  shows  no  trace  of  sulphates 
when  tested  with  BaCl2.  Now  pour  the  MgO  on  to  a  large 
filter,  let  it  drain  and  dry.  It  is  now  free  from  sulphur 
compounds. 

Ignite  the  dry  MgO  in  a  covered  platinum  crucible  until 
all  water  is  expelled.  Cool  and  weigh  it.  Now  add  half  its 
weight  of  previously  dried  C.  P.  Na2CO3.  Grind  the  two 
together  till  thoroughiy  mixed,  and  keep  in  a  tight  glass 
stopped  bottle. 

Of  course  if  a  sample  of  light  oxide  of  magnesia  can  be  obtained 
free  from  sulphur  the  above  is  unnecessary.  But  by  using  a  tin  bucket 
to  work  in  the  preparation  from  ordinary  material  is  easy  and  the  re- 
sults sure. 

Process  of  Analysis. — Weigh  one  grin,  of  the  coal  or 
coke  (which  must  be  finely  powdered,  especially  in  the  case 
of  coke),  then  weigh  out  roughly  two  grms.  of  the 


Notes  on  Metalhirgical  Analysis.  75 

"  Eschka  mixture."  Mix  about  two-thirds  of  this  with  the 
coal,  using  a  spatula  and  a  piece  of  glazed  paper.  Transfer 
this  to  a  30cc  platinum  crucible,  and  settle  it  down  by  tap- 
ping the  crucible  on  the  table.  Now  cover  the  contents  of 
the  crucible  with  the  remaining  portion  of  the  Eschka 
mixture. 

Set  the  crucible  in  an  inclined  position,  over  a  small 
alcohol  flame,  so  that  the  tip  of  the  flame  may  barely  touch 
the  crucible  near  the  top  of  the  mixture.  The  heat  must  be 
carefully  regulated,  so  that  no  blackening  of  the  white  cover 
layer  takes  place,  and  no  trace  of  smoke  appears.  The 
cover  should  be  set  in  the  mouth  of  the  crucible  to  assist 
the  draught.  The  mixture  soon  ignites  and  will  gradually 
burn  through,  as  may  be  observed  through  fissures  which 
open  in  the  mass.  -The  coal  will  usually  burn  completely  in 
less  than  an  hour.  The  heat  may  be  raised  toward  the  end 
of  the  combustion  and  the  lamp  set  back  under  the  bottom 
of  the  crucible.  A  higher  heat  may  be  used  with  cokes  from 
the  start,  as  these  give  no  volatile  products  and  burn 
slowly.  Finally  stir  up  the  powder  with  a  hot  glass  rod  or 
platinum  wire.  If  the  burning  is  complete  all  trace  of  the 
black  coal  will  have  disappeared  and  only  a  light,  reddish 
gray  mass  remain.  Cool  and  pour  the  powder  into  a  200cc 
beaker.  Add  about  lOOcc  of  boiling  water,  stir  and  digest 
on  a  water  bath.  Then  filter  and  wash  the  residue  thor- 
oughly with  hot  water. 

To  the  filtrate  add  bromine  water  until  the  liquid  is  col- 
ored yellow,  then  add  2  or  3cc  of  HC1  and  warm  until  all 
CO2  is  removed. 

Then  add  a  slight  excess  of  BaC12  solution,  and  let  the 
BaSO4  settle.  Filter,  wash,  dry,  ignite  and  weigh  as  BaSO4. 
Calculate  the  sulphur  as  5. 

Always  examine  the  residue  which  was  extracted  with  water,  by 
washing  it  off  the  filter  into  a  beaker,  and  then  adding  a  little  HC1 
and  warming.  All  will  dissolve  but  a  little  ash.  If  any  unburned  coal 
is  seen  in  the  residue,  the  analysis  must  be  repeated. 

Note. — The  above  is  by  far  the  neatest  and  quickest  method  for  sul- 


76  Notes  on  Metallurgical  Analysis. 

phur  determination  in  coals.  If  care  be  taken  in  all  details,  especially 
as  to  rate  of  heating,  there  is  no  loss  of  sulphur  whatever. 

It  has  been  proposed  to  substitute  K2CO3  for  the  Na2CO3,  and  said 
that  there  is  less  danger  of  loss  of  S  with  the  potassium  carbonate,  but 
the  writer's  experience,  extending  over  hundreds  of  analyses,  has  shown 
it  to  be  absolutely  unnecessary. 

The  use  of  alcohol  instead  of  gas  as  a  source  of  heat  is  essential. 
All  coal  gas  contains  sufficient  sulphur  to  vitiate  the  results. 

A  careful  "  blank  "  must  be  run  on  the  chemicals,  and  any  sulphur 
they  contain  deducted  from  that  found  as  above. 

Eschka,  Zeitschrift  An.  Chem.,  vol.  XIII,  p.  344. 
Drown,  Trans.  Am.  Inst.  Min.  Engs,.  vol.  IX,  p.  660. 

THE   ULTIMATE   ANALYSIS   OF   COAL. 

Determination  of  the  Carbon  and  Hydrogen  by  Combus- 
tion in  Oxygen. — 

The  coal,  placed  in  a  boat  of  porcelain  or  platinum,  is  burned  in  a 
combustion  tube,  through  which  a  current  of  purified  air  and  oxygen 
gas  is  passed.  The  H2O  and  CO2  produced  are  absorbed  and  weighed. 

The  only  difficulty  arises  from  the  presence  of  sulphur  in  the  coal, 
which  forming  SO2  would  pass  over  into  the  potash  bulbs  and  vitiate 
the  carbon  results.  This  is  prevented  by  the  use  of  lead  chromate 
which  oxidizes  and  holds  the  S  as  PbSO4. 

To  work  most  effectively  the  PbCrO4  must  be  kept  at  a  barely  vis- 
ible red  heat,  and  on  no  account  be  allowed  to  melt. 

The  process  is  difficult  only  in  that  it  requires  close  attention  to  de- 
tails and  skill  in  fitting  and  manipulating  apparatus. 

The  chemical  points  of  difficulty  are  as  follows :  First,  coal  begins 
to  decompose  at  a  low  temperature,  among  the  products  is  marsh  gas 
(CH4).  This  is  very  difficult  to  burn,  and  easily  escapes  from  the  com- 
bustion tube.  To  secure  its  oxidation  a  long  and  hot  layer  of  copper 
oxide  is  necessary.  Second,  the  oxygen  and  air  passed  through  the  ap- 
paratus may  easily  carry  in  hydrocarbon  vapors  taken  up  from  rubber 
connections,  these  becoming  oxidized  in  the  combustion  tube  lead  to 
false  results.  For  this  reason  the  oxygen  must  not  be  supplied  from 
rubber  gas  bags,  and  long  rubber  tubes  are  to  be  avoided.  Third,  the 
oxide  of  copper  and  asbestos  used  in  the  tube  must  be  free  from  CaCO3, 
or  other  carbonates  or  alkaline  bases.  Commercial  CuO  frequently  con- 
tains these  impurities.  These  carbonates  give  up  CO2  in  the  tube  on 
heating,  and  the  CaO  left  will  absorb  CO2  in  subsequent  tests.  Examine 
the  CuO  by  washing  with  a  little  cold  dilute  HNO3,  then,  after  neutral- 
izing with  NH4HO,  testing  the  liquid  with  ammonium  oxalate. 

The  asbestos  used  in  the  tube  must  be  first  freed  from  carbonates 
and  organic  matter  by  boiling  with  hydrochloric  acid,  washing  with 
water  until  free  from  acid  and  then  igniting  thoroughly  in  air. 


Notes  on  Metallurgical  Analysis.  77 

The  best  way  to  secure  a  pure  oxide  of  copper  is  that  proposed  by 
Blair.  Oxidize  fine  copper  gauze  by  heating  in  a  current  of  pure  oxygen. 

All  the  points  apply  here  that  were  mentioned  in  connection  with 
the  determination  of  carbon,  as  to  handling  and  arranging  the  absorp- 
tion apparatus. 

The  Apparatus  and  its  Arrangement. — First :  a  glass  or 
metal  gas  holder  containing  oxygen. 

This  may  be  cheaply  made  of  two  5-pin t  acid  bottles.  Bore  holes 
near  the  bottom  and  connect  the  two  by  a  rubber  tube.  One  bottle 
holds  water,  the  other,  provided  with  a  cork  and  exit  tube,  contains 
the  gas. 

About  50()cc  of  oxygen  will  be  required  for  a  combustion.  The  gas 
is  best  made  by  heating  a  mixture  of  KC1O3  with  one-third  its  weight 
of  MnO2  in  a  small  round-bottomed  glass  flask. 

Second ':  Purifying  Apparatus  for  the  Air  and  Oxygen, 
consisting  of:  A. — A  wash  bottle  with  a  three-hole  cork  and 
containing  50  or  75cc  of  a  clear  solution  of  KHO  of  1.27  sp. 
gr.  This  is  fitted  with  three  tubes.  One  for  oxygen,  connected 
with  the  gas  holder.  This  connection  must  be  of  glass  tubes 
and  made  flexible  by  one  or  two  short  rubber  joints  on  one 
of  which  is  put  a  pinch-cock  for  regulating  the  gas  supply. 
A  second  tube  allows  air  to  enter.  Both  these  tubes  dip 
deep  into  the  KHO  solution.  A  third  tube  conveys  the  gas 
and  air  from  the  bottle  to  the  next  point.  B. — A  U-tube 
filled  with  "  soda  lime."  C.— A  U-tube  filled  with  CaCl2. 

This  apparatus  frees  the  air  and  oxygen  from  all  traces  of  CO2  and 
moisture.  It  may  be  made  much  more  elaborate  where  it  is  to  be  used 
repeatedly,  as  this  simple  arrangement  will  be  soon  exhausted. 

Third :  A  Glass  Combustion  Tube  set  in  a  packing  of  as- 
bestos, in  the  trough  of  a  long  gas  combustion  furnace. 

This  must  be  of  the  best  infusible  glass.  It  should  have  an  internal 
diameter  of  about  one-half  inch,  and  the  glass  must  not  be  too  thick  or 
it  will  craek. 

The  ends  are  to  be  rounded  by  heat  and  stopped  with  good  soft 
corks  well  rolled.  Rubber  connections  with  this  tube  are  not  to  be 
recommended  as  they  become  warm  and  are  liable  to  give  off  hydro- 
carbon vapors. 

This  tube  is  filled  as  follows,  leaving  a  space  of  two  or 
three  inches  empty  at  each  end:  1. — A  plug  of  asbestos. 
2. — Six  inches  of  coarsely  powdered  fused  PbCrO4.  3.— 


78  Notes^on  Metallurgical  Analysis. 

Asbestos.  4. — Eight  inches  of  granular,  pure,  recently 
ignited  CuO  (or  a  close  coil  of  fine  copper  gauze  thor- 
oughly oxidized  by  heating  in  a  stream  of  pure  oxygen).  5. — 
Asbestos.  6.— The  "  boat  "  for  holding  the  coal.  7.— A  coil 
of  Cu  gauze  two  or  three  inches  long,  made  so  that  it  can  be 
easily  withdrawn  and  replaced.  This  must  be  thoroughly 
oxidized  before  using. 

The  end  of  this  tube  containing  the  movable  coil  and 
the  boat  are  connected  by  a  glass  tube  and  short  rubber  joint 
with  the  u  purifying  train  "  above. 

The  cork  connections  in  the  ends  of  this  tube  must  not  become  hot 
so  as  to  run  any  risk  of  burning,  hence  a  sufficient  length  of  empty  tube 
must  remain  at  each  end. 

Fourth :  The  Absorbing  Train  following  the  combustion 
tube  consisting  of:  A. — A  CaCl2  tube,  the  end  being  inserted 
into  the  cork  of  the  combustion  tube.  B. — Leibig's  potash 
bulbs.  C. — A  soda  lime — CaCl2  tube  similar  to  that  used  in 
connection  with  the  potash  bulbs  in  the  carbon  determina- 
tion. D. — A  guard  tube  and  aspirator. 

Testing  the  Apparatus. — First,  see  that  it  is  perfectly  tight  by  run- 
ning the  aspirator  and  shutting  off  the  entrance  of  air. 

Second.— Heat  the  tube  redhot  throughout  and  aspirate  two  litres. 
Detach  and  weigh  the  potash  bulbs  and  U-tube.  Connect  up  again  and 
aspirate  one-half  litre  of  oxygen  and  then  two  litres  of  air.  Detach  the 
tubes  and  weigh.  There  should  be  neither  gain  nor  loss  of  weight. 
When  these  tests  are  found  satisfactory  the  analysis  may  be  proceeded 
with. 

Process  of  Analysis. — Ignite  and  cool  the  boat.  Weigh 
into  it  0.2  grm.  of  the  finely  pulverized  and  mixed  coal.  (The 
sample  must  be  made  very  fine,  or  weighing  so  small  a  quan- 
tity will  not  give  average  results.)  Insert  the  boat  into  its 
proper  place.  Replace  the  coil  of  CuO  that  follows  it.  (This 
should  have  been  only  exposed  to  the  air  for  a  moment,  as  it 
readily  absorbs  moisture.) 

Connect  up  the  apparatus  and  then  carefully  heat  the 
PbCrO4  to  dull  redness  and  the  CuO  to  bright  redness,  draw- 
ing a  slow  current  of  air  through  the  apparatus  all  the  time. 
Now  begin  to  heat  the  coal  cautiously  and  introduce  oxygen, 


Notes  on  Metallurgical  Analysis.  79 

regulating  the  supply  so  as  to  avoid  too  vigorous  combustion 
and  consequent  fusion  of  the  ash,  which  will  lead  to  reten- 
tion of  carbon.  When  all  is  burned  cut  off  the  oxygen  and 
aspirate  air.  Turn  off  the  gas  burners  and  let  it  cool,  con- 
tinuing to  aspirate  air  until  two  or  three  litres  or  more  (at 
least  seven  times  the  capacity  of  the  whole  apparatus)  is 
drawn  through.  Now  detach  the  absorption  train  and  weigh. 
The  increase  of  the  CaCl2  tubes  gives  the  water  produced, 
which  divided  by  nine  gives  the  hydrogen  in  the  coal.  The 
increase  in  the  CO2  apparatus  the  CO2,  T3T  of  which  is  car- 
bon. The  apparatus  is  now  ready  for  another  determination, 
as  the  CuO  will  have  all  been  reoxidized. 

THE   DETERMINATION  OF   NITROGEN   IN  COAL. 

This  is  best  done  by  the  Kjeldahl  method  or  by  the  soda  lime 
method,  either  of  which  yields  correct  results,  provided  the  coal  be  in  very 
fine  powder  and  be  completely  oxidized.  In  the  Kjeldahl  method  the  sul- 
phuric acid  solution  of  the  coal  must  be  colorless  and  free  from  specks 
of  carbon.  The  time  required  to  accomplish  this  may  be  two  or  three 
hours,  but  it  can  always  be  done  and  is  essential. 

In  using  the  soda  lime  method  the  soda  lime  in  the  tube  must  be 
heated  until  it  becomes  white  and  all  carbon  has  disappeared,  so  that  on 
testing  by  solution  in  HC1  it  shows  no  remaining  carbon. 

Fault  has  been  found  with  the  soda  lime  method  for  nitrogen  in 
coals;  but  with  these  precautions  parallel  determinations  have  shown 
me  that  it  gives  the  same  results  as  the  Kjeldahl  and  the  so-called 
*' absolute"  method  of  Dumas. 

For  detailed  and  accurate  description  of  both  methods  see 

Bulletin  of  the  U.  S.  Dept.  of  Agriculture,  No.  31  or  35. 

(Report  of  the  Proceedings  of  the  Association  of  Official  Agricul- 
tural Chemists.) 

Tfie  Oxygen  in  Coal.—  This  is  estimated  by  difference,  subtracting 
the  sum  of  the  H.  N,  C.  S.  and  ash  from  100.  The  results  so  obtained 
are  open  to  criticism,  but  no  good  direct  method  is  known. 


THE    ANALYSIS    OF    FURNACE    AND    FLUE   GAS. 

The  principal  ingredients  are  CO2,  CO,  O  and  N.  In  addition  to 
these  there  are  small  percentages  of  H,  CH4,  C2H4,  H2S  and  occasion- 
ally other  gases. 

The  determination  of  the  CO2,  CO  and  O  is  all  that  is  usually  re- 


OF  THE 

UNIVERSITY 


80  Notes  on  Metallurgical  Analysis. 

quired  for  metallurgical    purposes,   the  residue    being    considered  as 
nitrogen. 

For  complete  information  on  the  subject  of  gas  analysis  the  student 
is  referred  to 

"Technical  Gas  Analysis,"  by  Clemens  Winkler.  Translated  by 
Lunge. 

"  Gas  Analysis,"  by  Hempel. 

The  process  for  the  determination  of  the  three  gases  named  consists 
in  treating  a  measured  volume  of  the  gas  with  a  series  of  reagents  which 
absorb  them  successively,  and  measuring  the  remaining  volume  each 
time. 

There  are  many  forms  of  apparatus  used  for  this  operation.  That 
the  results  may  be  accurate  it  is  desirable  that  the  tube  in  which  the 
gas  is  measured  be  surrounded  by  a  water  jacket.  This  serves  to  keep 
the  temperature  nearly  uniform.  By  placing  a  thermometer  in  the 
water,  any  variations  in  temperature  during  the  course  of  the  analysis 
may  be  noted  and  allowed  for,  by  correcting  the  corresponding  reading 
so  as  to  bring  it  to  what  it  would  have  been,  had  the  temperature 
remained  that  at  which  the  original  volume  was  measured.  This  can 

be  done  by  using  the  formula  V=V'— V'^Lr   -77,    in    which    V    is  the 

Z<o  -|-  I 

volume  at  the  temperature  t,  and  Vx  the  volume  at  the  temperature  V. 

To  avoid  calculation  the  gas  is  always  measured  at  the  atmospheric 
pressure,  to  which  it  is  brought  by  a  pressure  tube  or  bottle  connected 
with  the  reservoir  by  a  flexible  tube,  so  the  level  of  the  liquid  outside 
and  in  may  be  made  the  same. 

Variations  of  the  barometer  are  not  considered,  as  they  are  rarely 
important  during  the  short  time  the  analysis  covers. 

Collecting  the  Gas  for  Analysis. — Take  two  quart  bottles, 
bore  a  hole  in  each  near  the  bottom  and  connect  them  by  a 
rubber  tube.  Fit  one  with  a  rubber  cork  and  glass  tube,  to 
which  attach  a  small  rubber  tube  closed  by  a  good  pinch- 
cock.  Put  into  the  bottles  a  saturated  solution  of  salt  (NaCl), 
so  that  by  elevating  the  open  one  the  other  can  be  completely 
filled  (rubber  tube  and  all).  Now  attach  the  rubber  tube  to 
an  iron  tube,  reaching  well  into  the  gas  main.  Lower  the 
empty  bottle,  open  the  pinch-cock  and  let  the  liquid  slowly 
run  out  of  the  full  bottle,  drawing  the  gas  after  it.  When  it 
is  full  close  the  cock  and  disconnect  from  the  gas  tube. 

Furnace  and  all  gases  rich  in  CO2  are  rapidly  changed  by  standing 
in  contact  with  water,  in  which  the  CO2  is  quite  soluble.  Salt  both 


Notes  on  Metallurgical  Analysis.  81 

diminishes  this  solubility  and  makes  the  absorption  much  slower.   Such 
gases  should  be  analyzed  as  soon  as  possible  after  the  sample  is  drawn. 

Troilius  Notes  on  Chem.  of  Iron,  p.  76. 

Samples  cannot  be  kept  unaltered  in  rubber  bags. 

Determination  of  CO.2,  CO,  and  O,  with  A.  H.  Elliots 
Apparatus. — 

This  is  one  of  the  simplest  and  most  easily  handled  of  the  various 
forms  of  absorption  apparatus.  It  consists  of  a  graduated  measuring 
tube  connected  by  a  capillary  tube  and  stopcock,  with  a  plain  tube  in 
which  the  gas  can  be  treated  with  the  various  absorbents. 

It  is  figured  in  the  catalogues  of  most  dealers  in  chemical  glass- 
ware. 

It  should  be  provided  with  the  water  jacket  and  thermometer. 

For  full  description  see 

Chemical  News,  vol.  XLVIII,  p.  189;  also  School  of  Mines  Quarterly,  Nov.,  1881. 

The  Reagents  used  for  Absorption  are  as  follows :  They  must  be 
applied  in  the  order  given,  as  some  will  absorb  other  gases  besides  the 
special  one  intended,  unless  such  were  first  removed. 

1.  Absorbent  for  CO2. — A  16  per  cent,  solution  of  caus- 
tic potash  (KHO).      This  acts  very  rapidly  and  completely. 
It  also  absorbs  H2S  and  SO2,  if  present  in  the  gas. 

2.  Absorbent  for  Oxygen. — An  alkaline  solution  of  py- 
rogallic  acid.     Dissolve  twenty  grms.  of  pyrogallic  acid  in 
lOOcc  of  water.     This  solution  keeps  fairly  well  if  in  tight 
bottles.     When  about  to  use  it    mix  some  of  this  solution 
with  its  own  volume  of  the  potash  solution. 

This  mixture  absorbs  oxygen  very  rapidly  at  first,  but  only  takes 
out  the  last  trace  after  somewhat  prolonged  contact  with  the  gas.  Hence 
after  absorbing  most  of  the  oxygen,  add  a  little  fresh  solution,  and  let 
it  act  ten  or  fifteen  minutes  longer. 

3.  Absorbent  for  Carbonic  Oxide. — A  strongly  acid  solu- 
tion of   cuprous  chloride.      Dissolve  fifteen  grms.  of  "  red 
oxide  of  copper  "  (Cu2O)  in  lOOcc  of  strong  HC1  (sp.  gr.  1.19). 
Keep  the  solution  in  a  glass  stoppered  bottle,  with  scraps  of 
metallic  copper. 

The  pure  solution  is  colorless.  Oxygen  turns  it  dark  brown.  This 
solution  absorbs  CO  quite  rapidly,  but  only  completely  when  in  vei*y 
large  excess.  The  best  way  to  use  the  reagent  is  to  add  successive  por- 
tions of  the  fresh  solution,  so  the  last  used  will  have  only  the  residual 


82  Notes  on  Metallurgical  Analysis. 

CO  to  absorb.  This  reagent  must  be  applied  after  the  O  is  removed,  as 
it  absorbs  it  also. 

When  mixed  with  water  this  solution  deposits  Cu2Cl2  as  a  sandy, 
insoluble  white  powder,  which  can  only  be  dissolved  out  of  the  appar- 
atus by  HC1. 

Ihe  following  Absorbents  are  also  occasionally  used :  Solution  of 
silver  nitrate  absorbs  H2S  only.  Solution  of  iodine  in  iodide  of  potas- 
sium and  water  (about  3  per  cent,  of  iodine)  absorbs  H2S  and  SO2. 
Bromine  water  absorbs  ethylene  (and  others  of  the  series)  ;  also  H2S 
and  SO2.  When  this  reagent  has  been  used,  the  bromine  vapor  must 
be  removed  (before  the  gas  is  measured)  by  potash  solution. 

Process  for  Analysis. — Transfer  the  gas  to  the  measuring 
tube.  Raise  the  pressure  bottle  until  the  liquid  in  it  and  in 
the  tube  are  at  a  level.  Now  read  the  volume.  Do  this  at 
intervals  of  a  minute  until  the  readings  do  not  change,  read 
and  record  the  thermometer.  Now  transfer  the  solution  to 
the  absorbing  tube  and  let  the  liquid  absorbent  run  slowly 
down  the  sides  of  the  tube  until  no  further  contraction  is 
observed  on  standing  three  or  four  minutes.  Add  water  to 
the  funnel  of  the  absorption  tube  and  let  it  run  through  until 
the*  reagent  is  washed  down.  Do  this  gently,  avoiding  all 
"splashing."  Now  transfer  the  gas  back  to  the  measuring  tube 
and  measure  as  before.  Record  the  thermometer  each  time 
and  reduce  all  readings  to  the  initial  temperature  by  the 
formula  given. 

When  the  gas  is  in  the  measuring  tube  and  the  stopcock 
connecting  it  with  the  absorption  tube  closed,  empty  the 
latter  and  wash  it  out.  Now  fill  it  with  water,  transfer  the 
gas,  and  proceed  with  the  next  reagent  in  exactly  the  same 
way.  Finally,  calculate  the  successive  losses  of  volume  into 
percentages  of  the  original  volume. 

Extreme  care  should  be  taken  to  avoid  getting  any  of  the  absorption 
solutions  into  the  measuring  tube.  Should  this  happen  the  whole  ap- 
paratus must  be  carefully  washed  out  before  starting  a  new  analysis,  as 
the  action  on  the  CO2  especially  will  cause  loss. 


on  Metallurgical  Analysis.  83 

THE  ANAI.Y7SIS  OF  BI^ASX  FURNACE  SLAGS. 

Most  slags  can  be  dissolved  by  hydrochloric  acid,  especially  if  they 
have  been  suddenly  cooled  from  the  melted  state. 

The  few  slags  which  are  not  attacked  by  acids  must  be  decomposed 
by  fusion  with  carbonate  of  soda.  (See  analysis  of  fire  clays.) 

It  is  frequently  necessary  to  know  the  silica,  alumina,  lime  and 
magnesia  in  a  slag.  The  following  process  is  rapid  and  will  give  suf- 
ficiently accurate  results  for  furnace  control. 

Determination  of  CaO  and  MgO. — Weigh  one  grin,  of 
the  finely  pulverized  slag.  Add  to  it  30cc  of  water.  Stir  it 
well  up  in  the  water,  so  that  there  may  be  no  "  caking''  on 
addition  of  acid.  This  is  important,  for,  if  the  acid  be  added 
to  the  slag  while  in  a  compact  mass  on  the  bottom  of  the 
dish,  it  is  at  once  covered  with  a  coat  of  gelatinous  silica, 
which  prevents  solution. 

Now  add  20cc  of  HC1  and  heat  until  all  is  dissolved,  ex- 
cept a  few  flakes  of  SiO2and  carbon  or  sulphur,  and  no  gritty 
residue  remains.  Cover  and  boil  to  dryness.  Heat  carefully 
till  the  HC1  is  expelled.  Then  add  lOcc  of  HC1  and  50cc  of 
water.  Boil,  transfer  without  filtering  to  a  500cc  flask  and  add 
lOcc  more  HC1.  Dilute  till  the  flask  is  two-thirds  full  and  add 
NH4HO  till  the  alumina  is  precipitated,  but  avoid  a  large 
excess.  Dilute  the  flask  to  the  mark,  mix  well  and  let  settle. 
Filter  off  200cc  through  a  dry  filter. 

In  this,  precipitate  the  CaO  as  oxalate  and  then  the  MgO 
as  phosphate  exactly  as  in  the  filtrate  from  the  A12O3,  Fe2O3 
in  the  analysis  of  limestones.  Calculate  the  results  on  0.4 
grrns.  taken. 

The  precipitate  of  calcium  oxalate  may  be  estimated  volumetric- 
ally  with  potassium  permanganate.  See 

Fresenius  Quant.  Analysis  Determination  of  CaO. 

Determination  of  SiO2  and  A!2O3. — Weigh  another  por- 
tion of  0.5  grm.  Treat  it  with  water  and  HC1  as  before. 
Dry  and  add  HC1  and  water,  boil,  filter  and  wash.  Ignite 
and  weigh  the  residue,  which  may  be  taken  as  silica. 

It  may  be  tested  by  adding  H2SO4  and  HF1,  and  after  driving  oft 
the  SiO2,  igniting  and  weighing  the  residue,  which  should  be  deducted 
from  the  total  weight.  (Blair  Chem.  An.,  Iron.)  As,  however,  the  sil- 


84  Notes  on  Metallurgical  Analysis. 

ica  is  never  completely  separated  by  a  single  evaporation,  the  impurities 
present  will  about  balance  the  silica  lost,  so  that  for  ordinary  furnace 
control  the  gross  weight  will  be  reasonably  accurate. 

To  the  filtrate  from  the  silica  add  20cc  of  HC1,  then  a 
slight  excess  of  ammonia.  The  solution  should  be  diluted 
to  about  200cc,  warmed  but  not  boiled  and  let  settle.  The 
clear  liquid  is  decanted  and  the  precipitate,  washed  by  decan- 
tation  twice,  using  warm  water.  The  liquid  decanted  off  need 
not  be  filtered  ;  it  should  be  perfectly  clear.  Now  add  to  the 
precipitate  lOcc  more  HC1,  which  will  dissolve  it.  Dilute 
to  200cc  and  again  precipitate,  and  wash  by  decantation  till 
free  from  HC1.  Finally  transfer  to  a  filter,  dry,  ignite  and 
weigh  as  A12O3.  The  precipitate  contains  iron,  phosphoric 
acid  and-titanic  acid,  but  these  bodies  being  only  present  in 
traces  in  ordinary  slags,  may  be  neglected. 

The  alumina  precipitate  as  above  obtained  can  be  handled  rapidly. 
A12O3  is  completely  precipitated  by  NH4HO  without  boiling  in  solu- 
tions containing  a  large  excess  of  NH4C1,  and  when  so  precipitated  set- 
tles easily. 

Lunge,  Jour.  Soc.  Chem.  Inds.,  vol.  IX,  p.  111. 

The  above  scheme  for  CaO  fails  when  the  slag  contains  much 
manganese.  This  will  come  down  in  part  writh  the  magnesia  and 
partly  separate  with  the  iron  and  alumina  in  the  500ce  flask. 

In  this  case,  after  solution  of  the  evaporated  mass  in  HC1,  dilute  to 
200cc,  and  add  carbonate  of  sodium  till  a  slight  precipitate  forms.  Re- 
dissolve  this  with  a  drop  or  two  of  HC1,  then  add  3  grins,  of  sodium 
acetate  and  boil  till  the  A12O3  separates.  Dilute  to  SOOcc,  mix  and  set- 
tle as  before.  Filter  off  200cc.  Add  5  grms.  of  sodium  acetate  then 
bromine  water  and  determine  the  manganese  as  in  iron  ores.  Treat  the 
filtrate  from  the  manganese  for  CaO  and  MgO  as  before. 

Sulphur  and  iron  are  to  be  determined  in  slags  as  in  iron  ores. 

The  sulphur  in  slags  is  present  principally  as  calcium  sulphide.  It 
may  be  determined  approximately  by  adding  150cc  of  water  to  0.5  grm. 
of  the  very  finely  pulverized  slag  and  titrating  with  the  standard  iodine 
solution  used  for  sulphur  in  iron. 

Stir  the  mixture  of  slag  and  water  well,  add  3  or  4cc  of  starch  solu- 
tion, then  run  in  the  iodine  till  the  blue  color  develops.  Now  add  15cc 
of  cone.  HC1,  stir  and  add  the  iodine  again  until  the  color  no  longer  dis- 
appears. 

If  Ice  of  the  iodine  equals  .0005  S,  each  cc  taken  will  be  equivalent 
to  0.1%  sulphur  in  the  slag. 

Jour.  An.  and  App.  Chem.,  vol.  VII,  No.  5. 


Notes  on  Metallurgical  Analysis.  86 

THE   ANALYSIS  OF    FIR  1C    CI.AYS. 

Determination  of  SiO.2,  Al^O^  Fe^O^  CaO  and  MgO. — 
Take  1  grm.,  mix  it  with  8  grms.  of  dry  Na2CO3.  Put  the 
mixture  in  a  platinum  crucible,  and  heat  over  a  Bunsen 
burner  until  the  mass  is  shrunken  together  and  caked.  Now 
apply  a  blast  lamp  and  rapidly  fuse.  Keep  some  minutes  in 
quiet  fusion.  Cool  suddenly  by  dipping  the  bottom  of  the 
crucible  into  water  (this  will  usually  cause  the  cake  of  ma- 
terial to  come  loose  so  that  it  can  be  easily  detached  from 
the  crucible).  Now  put  the  cake,  with  the  crucible,  into  a 
dish  or  caserole  with  water  enough  to  cover  the  whole,  and 
wash  the  cover  of  the  crucible  free  from  all  attached  par- 
ticles. As  soon  as  all  is  disintegrated,  remove  the  crucible, 
cleaning  it  if  necessary  with  a  little  HC1,  which  is  then  to  be 
added  to  the  body  of  the  liquid.  Now  add  an  excess  of  HC1 
to  the  contents  of  the  dish,  which  must  be  kept  carefully 
covered  to  avoid  loss  by  "  spurting."  Warm  until  everything 
is  dissolved  and  effervescence  has  stopped.  Wash  off  the 
cover  and  evaporate  the  liquid  to  dryness  on  a  water  bath, 
stirring  occasionally  to  break  up  the  jelly.  When  all  odor 
of  HC1  has  ceased,  add  a  little  water  and  again  evaporate  to 
dryness.  Now  add  30cc  of  dilute  HC1  (1  :  1)  digest  at  a 
gentle  heat,  and  then  dilute  to  150  or  200cc,  filter  and  wash 
thoroughly,  ignite  and  weigh  repeatedly  until  the  weight  is 
constant.  The  residue  is  SiO2  —  its  purity  must  be  tested  by 
volatilizing  it  by  HF1  and  H2SO4,  or  by  re-fusion  with  Na2 
CO3,  and  repeating  the  separation. 

The  filtrate  should  be  diluted  to  300cc,  warmed  and  pre- 
cipitated by  a  slight  excess  of  NH4HO.  Warm  until  the 
precipitate  has  settled,  leaving  a  perfectly  clear  liquid.  De- 
cant this  off  as  far  as  possible  without  disturbing  the  precip- 
itate (the  use  of  a  siphon  for  this  purpose  is  often  advan- 
tageous). Fill  up  to  about  250cc  with  hot  water  and  lei  set- 
tle again.  Decant  this  in  the  same  way.  Repeat  this  until 
the  liquid  decanted  off  no  longer  reacts  for  HC1  with  AgNO3. 


86  Notes  on  Metallurgical  Analysis. 

Finally  transfer  the  precipitate  of  A12O3  +  Fe2O3  (+.TiO2 
-f  traces  of  SiO2)  to  a  filter  (do  not  wash  on  the  filter)  dry, 
transfer  the  precipitate  to  a  crucible,  carefully  burn  the 
paper  separate,  add  the  ash  to  the  crucible,  ignite  strongly 
and  weigh. 

After  weighing,  brush  the  A12O3,  etc.,  out  into  a  small 
beaker,  cover  it  with  a  mixture  of  strong  H2SO4  8  parts, 
water  3  parts,  and  digest  on  a  hot  plate  for  some  time.  All 
will  dissolve  but  a  slight  residue  of  SiO2.  Dilute  the  liquid, 
then  filter  off  and  weigh  this ;  it  is  to  be  deducted  from  the 
weight  of  the  precipitate  first  obtained.  In  the  liquid  deter- 
mine the  iron  volumetrically,  as  in  iron  ores,  calculate  it  as 
Fe2O3  and  deduct  this,  and  the  remainder  will  be  A12O3. 

Collect  all  the  washings  from  the  A12O3  except  the  first, 
separate  from  the  first  liquid  decanted  off,  boil  them  down 
rapidly  in  a  large  porcelain  dish  to  a  small  bulk  and  transfer 
them  to  a  beaker.  Now  add  a  few  drops  of  NH4HO  and 
filter  from  any  trace  of  A12O3  separating,  use  a  small  ashless 
filter.  Add  this  filtrate  to  the  first  portion  which  was  not 
boiled  down,  and  the  precipitate  to  the  main  portion  of  the 
A12O3.  Should  the  liquid  settle  badly  as  the  washing  pro- 
ceeds, add  2  or  3  drops  of  NH4HO,  which  will  cause  it  to 
clear  promptly. 

Now  concentrate  the  total  filtrate  from  the  A12O3  to 
about  200cc  on  a  water  bath  and  determine  the  CaO  and 
MgO  exactly  as  in  the  analysis  of  a  limestone. 

Determination  of  the  Alkahes  by  J.  Lawrence  Smith's 

Method.— 

When  silicates  containing  K2O  and  Na2O  are  heated  with  a  mix- 
ture of  CaCO3  and  NH4C1,  CaCl3  is  first  formed  by  double  decomposi- 
tion, and  this  then  acts  on  the  silicates  forming  alkaline  chlorides  and 
lime  silicates.  A  red  heat  is  necessary. 

There  is  needed  pure  CaCO3,  free  from  K2O  and  Na2O.  This  can 
be  prepared  by  dissolving  marble  in  HC1,  to  saturation,  adding  a  little 
slaked  lime  to  make  the  liquid  alkaline  and  precipitate  Fe2O3,  A12O3  and 
P2O5,  then  diluting  and  heating  the  liquid  and  precipitating  the  CaCO3 
by  (NH4)2  CO3.  This  is  washed  till  free  from  HC1  and  dried.  Second, 
pure  NH4C1.  This  must  be  powdered  and  must  volatilize  without  re- 
sidue at  a  low  red  heat. 


Notes  on  Metallurgical  Analysis.  87 

Process. — Mix  one  grm.  of  clay  with  one  grm.  of  NH4C1. 
Grind  them  together  in  a  small  porcelain  mortar.  Add 
eight  grms.  of  CaCO3  and  mix  thoroughly  with  the  clay  and 
CaCO3.  Take  a  large  (30-50cc)  platinum  crucible,  put  a  little 
pure  CaCO3  on  the  bottom,  and  then  add  the  mixture.  Clean 
out  the  mortar  by  grinding  a  little  more  CaCO3  in  it.  Add 
this  on  top  of  the  mixture  as  a  cover. 

Now  cover  the  crucible  and  heat  carefully,  gently  at  first, 
but  gradually  to  full  redness  for  an  hour.  Cool  and  transfer 
the  sintered  mass  to  a  beaker.  Wash  the  crucible  and  cover 
with  hot  water  and  add  the  washings.  Digest  the  whole 
until  the  mass  slakes  down  to  a  fine  powder.  Now  filter  and 
wash  with  hot  water  until  the  filtrate  is  free  from  Cl. 

To  the  filtrate  add  NH4HO  and  (NH4)2  CO3  in  excess. 
The  calcium  separates  as  carbonate,  which  on  warming  be- 
comes granular  and  easily  filtered.  Filter  and  wash  with 
water  containing  a  very  little  NH4HO. 

Evaporate  the  filtrate  to  a  few  cc's  in  the  beaker,  then 
transfer  it  to  a  small  porcelain  dish  and  finally  bring  it  to 
dryness. 

Now  ignite  it  carefully  at  a  heat  not  exceeding  a  barely 
visible  red,  until  all  NH4C1  is  expelled  and  no  more  fumes 
form.  Cool  and  add  a  little  water  and  a  few  drops  of  (NH4)2 
CO3,  and  filter  from  any  residue.  Add  two  or  three  drops  of 
HC1  to  the  filtrate.  Again  evaporate  to  dryness  in  a  weighed 
porcelain  dish.  Dry,  ignite  carefully  as  before  and  weigh  as 
KC1  +  NaCl.  The  chlorides  must  be  white  and  dissolve 
without  residue  in  water. 

To  the  water  solution  add  an  excess  of  platinum 
chloride,  and  evaporate  carefully  to  nearly  dryness.  Add 
20cc  of  alcohol  (80  per  cent.)  and  let  stand  till  the  Na  salts 
dissolve.  Filter  on  to  a  weighed  filter.  Wash  the  K2PtCl6 
with  80  per  cent,  alcohol.  Dry  and  weigh.  Calculate 
the  K2O  from  the  weight  of  this  and  the  Na2O  from  the  re- 
mainder of  the  mixed  chlorides  after  deducting  the  KC1  cal- 
culated from  the  K2O. 


88  Notes  on  Metallurgical  Analysis. 

The  strength  of  the  alcohol  is  important.  The  K2PtCl6  is 
practically  insoluble  in  80  per  cent,  alcohol,  but  the  Na2PtCl6  will 
dissolve  in  it.  Time  must  be  given  to  secure  complete  solution  of  this 
latter  salt. 

Titanium  may  be  determined  in  fire  clay  as  in  the  insoluble  residue 
from  titaniferous  iron  ores. 

Clay  contains  silica  as  fine  sand  or  quartz,  also  silica  in  combina- 
tion with  alumina.  It  is  sometimes  desirable  to  find  the  amounts  of 
these  separately.  The  quartz  is  insoluble  in  potash  solution,  while  the 
SiO2  left  after  evaporation  of  solutions  of  silica  in  HC1  is  soluble,  also 
that  from  the  decomposition  of  silicates  by  H2SO4. 

Process  for  Determination  of  Free  and  Combined  Silica. — Treat  1 
grm.  of  the  clay  with  1©  or  15cc  of  cone.  H2SO4.  Heat  to  near  the 
boiling  point  of  the  acid  and  digest  for  12  hours.  Cool,  dilute,  filter, 
wash,  ignite  to  constant  weight. 

The  residue  consists  of  SiO3  as  sand,  SiO2  from  the  decomposition 
of  the  silicates  of  alumina  and  some  insoluble  silicates.  Transfer  to  an 
agate  mortar,  grind  fine,  brush  on  to  a  watch  glass  and  weigh  again. 

Heat  50cc  of  a  15%  solution  of  KHO  to  boiling  in  a  platinum  dish. 
Add  the  above  weighed  residue  and  boil  five  minutes.  Again  filter, 
wash,  ignite  and  weigh.  The  silica  which  had  been  separated  from  the 
alumina  will  have  dissolved  the  residue  being  sand  and  silicates.  De- 
duct this  weight  (calculated  to  the  whole  residue)  from  the  original 
weight  of  residue  and  the  difference  will  be  the  combined  silica.  This 
in  turn  deducted  from  the  total  silica,  regularly  determined,  gives  the 
silica  as  sand  and  undecomposable  silicates. 

The  above  scheme  for  fire  clay  analysis  avoids  the  use  of  hydro- 
fluoric acid.  Where  that  is  available  the  decomposition  of  the  clay  by 
its  use  both  for  alumina  and  alkalies  is  more  rapid. 

See  Blair,  Chem.  An.  Iron  and  Steel,  Second  Edition. 


mi;  I>I;TI:KMIX ATIO:N  OF  COPPER  IK  ORBS. 

Most  copper  ores  are  dissolved  by  digestion  with  cone.  HNO3. 
Sulphur  may  separate,  but  will  be  practically  free  from  copper.  Some 
few  bodies  (as  slags)  may  require  to  be  fused  with  sodium  carbonate  and 
nitrate. 

The  most  generally  reliable  method  for  the  determination  of  cop- 
per is  by  electro-deposition.  The  conditions  most  favorable  are :  a  suf- 
ficiently dilute  solution ;  not  too  much  free  acid,  and  not  too  strong  a 
current,  failure  in  these  will  cause  the  copper  to  be  spongy,  dark  colored 
and  difficult  to  wash. 

Hydrochloric  acid  must  be  absent ;  also  much  nitric  acid.  Presence 
of  much  arsenic,  antimony  or  silver  will  cause  the  copper  to  be  impure. 
Bismuth  is  especially  hurtful,  very  small  percentages  causing  the  re- 


Notes  on  Metallurgical  Analysis.  89 

suits  to  be  high.  Should  these  elements  be  present  in  the  ores  they 
must  be  removed  before  precipitating  the  copper.  They  are  rarely 
present  in  ordinary  ores  in  quantity  sufficient  to  influence  the  results. 

Process  for  Copper  Ores. — Take  an  amount  of  ore  which 
shall  not  contain  more  than  0.200  grms.  of  Cu.  It  must  be 
very  finely  pulverized.  Put  it  in  a  small  beaker,  add 
5cc  HNO3,  5cc  HC1  and  5cc  H2SO4.  Cover  with  a  watch 
glass  and  boil  until  the  ore  is  decomposed,  all  the  HC1  and 
HNO3  are  expelled  and  white  fumes  of  H2SO4  begin  to  ap- 
pear. Cool,  dilute  to  50cc  and  boil,  filter  and  wash.  The 
residue  should  be  light  colored  and  must  be  tested  for  copper 
with  the  blow-pipe. 

Put  the  solution  in  a  weighed  platinum  dish  of  lOOcc 
capacity.  Connect  the  dish  with  the  zinc  side  of  a  battery 
of  two  gravity  cells  or  its  equivalent,  and  introduce  into  the 
solution  a  platinum  plate  connected  with  the  copper  end 
of  the  battery.  The  deposition  begins  at  once  and  is  com- 
plete in  seven  or  eight  hours.  When  all  trace  of  blue  color 
is  gone  from  the  solution,  take  out  a  few  drops  with  a  pipette 
and  test  with  H2S  water.  If  no  tinge  of  brown  is  produced 
the  Cu  is  all  down.  Empty  the  dish,  wash  it  carefully  first 
with  distilled  water,  then  with  strong  alcohol.  Dry  the 
alcohol  off  carefully,  avoiding  a  temperature  much  above 
100°C  and  weigh  the  dish  plus  the  copper. 

The  alcohol  may  be  lighted  and  u  burned  off"  without  danger,  and 
the  heat  thus  developed  will  dry  the  dish.  The  copper  must  be  red,  co- 
herent and  metallic.  A  slight  brownish  discoloration  will  not  be  of  per- 
ceptible influence  on  the  results.  See 

Peter's  "American  Methods  of  Copper  Smelting,"  p.  25;  also  W.  Lee  Brown,  Assaying, 
p.  333,  et  seq. 

THE   IODINE   METHOD   FOR   COPPER. 

This  is  much  more  rapid  than  the  electrolytic  method,  and  when 
carefully  conducted  gives  very  accurate  results.  It  depends  on  the 
fact  that  when  a  cupric  salt  is  treated  with  potassium  iodide  cuprous 
iodide  is  formed  and  iodine  liberated.  The  iodine  is  then  estimated 
volumetrically  with  sodium  hyposulphite.  The  conditions  are  a 
slightly  acid  solution  and  absence  of  considerable  amounts  of  sodium 
acetate.  Iron  must  be  absent  and  also  any  considerable  amount  of  anti- 
mony or  bismuth. 


90  Notes  on  Metallurgical  Analysis. 

Preparation  of  the  " Hypov  Solution.— Dissolve  39.18 
grms.  crystallized  sodium  hyposulphite  in  water  and  dilute 
to  one  liter.  Ice  equals  0.01  grms.  of  copper. 

The  reactions  from  which  this  is  calculated  are  as  follows :  2  CuSO4 
+  4  KI  =  Cu2I2  +  21  +  2  K2SO4  and 2  Na2S2O3  +  21  =  2  Nal  +  Na2 
S4O6.  The  crystallized  hyposulphite  contain  five  molecules  of  water. 
(Na2S203,  5H20.) 

Standardize  the  solution  against  pure  copper  or  pure  copper  sul- 
phate. Dissolve  the  copper  in  5cc  of  dilute  nitric  acid  (1  to  1),  boil  off 
all  nitrous  fumes  (this  is  essential  or  they  would  liberate  iodine)  dilute 
with  an  equal  bulk  of  water  and  add  a  solution  of  NaHO  cautiously 
until  a  permanent  precipitate  is  just  produced.  Now  add  Ice  of  acetic 
acid,  which  must  give  a  clear  solution ;  if  the  liquid  is  ivarm  cool  it.  Now 
add  3  grms.  of  pure  potassium  iodide.  When  it  is  dissolved  dilute  to 
lOOcc.  Now  run  the  hypo  solution  from  a  burette  until  the  brown  color 
due  to  the  liberated  iodine  is  nearly  discharged.  Then  add  2  or  3cc  of 
starch  solution  and  continue  to  add  the  hypo  until  the  blue  color  is  gone 
and  does  not  return  on  standing  four  minutes.  The  number  of  cc  of 
hypo  used  will  be  equivalent  to  the  copper  taken. 

Process  for  Ores. — Take  2  grms.  ore  (very  finely  pow- 
dered). Heat  in  a  small  covered  beaker  or  caserole  with 
20cc  of  cone.  HNO3.  When  violent  action  has  ceased  boil 
down  to  dryness.  Take  up  with  30cc  cone.  HC1,  digest  and 
dilute  to  200cc  without  filtering.  Warm  and  pass  a  rapid 
current  of  H2S  through  the  solution  till  the  Cu  is  all  down  as 
sulphide.  Filter  and  wash  with  water  containing  a  little 
H2S.  Wash  the  precipitate  back  into  the  beaker  or  dish.  If 
more  than  a  trace  remains  on  the  filter,  burn  it  and  add  the 
ash  to  the  rest.  Now  add  15cc  of  cone.  HNO3  and  boil 
almost  to  dryness.  Add  20cc  of  water  and  boil  till  all  nitrous 
fumes  are  expelled.  Filter  from  the  gangue  and  sulphur. 
Neutralize  the  solution  with  NaHO  solution  as  before.  Cool 
it  and  add  5  grms.  of  KI,  dilute  to  lOOcc  and  titrate  with  the 
hypo  solution.  The  sulphur  and  gangue  on  the  filter  should 
be  burned  off  in  a  porcelain  crucible  and  the  residue  ex- 
amined for  copper. 

See  "A  Text  Book  of  Assaying,"  C.  and  J.  J.  Beringer,  p.  159,  et.  seq. 


Notes  on  Metallurgical  Analysis.  91 

TUB  ASSAY  OP  ORBS  FOR  ZINC. 

Zinc  usually  occurs  in  ores  as  sulphide,  oxide,  carbonate  or  hydro- 
silicate. 

All  of  these  are  decomposed  by  boiling  with  acids,  the  zinc  passing 
into  solution.  When  sulphur  is  present  it  can  be  oxidized  by  HNO3 
andKC!O3. 

Acid  solutions  of  zinc  in  HC1  are  completely  precipitated  by  potas- 
sium ferrocyanide.  Iron,  copper,  cadmium  and  manganese  are  also  pre- 
cipitated in  the  same  way,  and  if  present  must  be  removed  from  the  so- 
lution before  the  zinc  is  determined. 

An  excess  of  ferrocyanide  in  the  solution  can  be  recognized  by  the 
brown  precipitate  it  gives  with  a  solution  of  urauic  nitrate  or  acetate 
(uranic  ferrocyanide).  This  reaction  is  less  sharp  in  acid  solution,  but 
by  using  a  concentrated  solution  of  the  uranium  salt,  and  only  a  little 
of  the  solution  to  be  tested,  is  still  sufficiently  delicate. 

The  HC1  solution  must  be  free  from  Cl  or  oxide  of  chlorine,  as 
these  decompose  the  ferrocyanide  and  liberate  iron  salts. 

PROCESS  OF  VON  SCHULZ  AND  LOW. 

Solution  of  the  Ore  and  Separation  of  the  Fe,  Mn  and 
Cu. — Weigh  one  grm.  into  a  4-inch  caserole.  Add  2  or  3cc 
of  cone.  HNO3,  then  cautiously  25cc  of  HNO3,  previously 
saturated  with  KC1O3  by  shaking  up  with  crystals  of  the 
salt.  (Keep  this  solution  in  an  open  bottle).  When  the 
violent  action  is  over,  cover  the  caserole  and  boil  rapidly  to 
dryness.  Do  not  bake  the  residue.  Now  cool  and  add  seven 
grms.  of  NH4C1,  25cc  of  hot  water  and  15cc  of  strong 
NH4HO.  Boil  the  liquid  one  minute  and  then  rub  the  dish 
with  a  rubber  tipped  rod  to  loosen  and  disintegrate  all  the 
insoluble  matter.  Filter  and  wash  several  times  with  a  boil- 
ing hot  1  per  cent,  solution  of  NH4C1.  If  the  filtrate  is  blue 
it  contains  Cu. 

Add  to  the  filtrate  25cc  of  cone.  HC1  and  dilute  to  200cc. 
If  Cu  is  present  add  forty  grms.  of  u  granulated  lead  "  and 
stir  until  the  liquid  is  colorless. 

The  zinc  salts  are  soluble  in  NH4HO,  while  the  Fe2O3,  A12O3,  etc., 
are  precipitated.  This  separation  is  quite  satisfactory  for  ores  contain- 
ing moderate  percentages.  When  much  zinc  is  present  or  much  iron, 
the  residue  may  retain  enough  to  affect  the  results  1  or  2  per  cent.  In 


92  Notes  on  Metallurgical  Analysis. 

this  case  it  must  be  dissolved  in  10  or  15cc  of  HC1,  and  reprecipitated  by 
NH4HO. 

This  second  filtrate  will  contain  Mn  if  present  in  the  ore.  To  re- 
move it  add  5  or  lOcc  of  hydrogen  peroxide  (H2O2)  and  filter  from  the 
MnO2.  Add  this  filtrate  to  that  from  the  main  quantity. 

The  HNO3  and  KC1OS  separate  all  the  Mil  in  the  first  case  as 
MnO2.  but  this  dissolves  in  the  HC1  again. 

It  is  essential  that  all  the  KC1O3  be  decomposed  and  the  Cl  driven 
off  in  the  evaporation,  as  if  any  gets  into  the  final  solution  for  titration 
it  will  cause  the  solution  to  become  blue  and  use  up  some  ferrocyanide. 

This  may  be  prevented  by  somewhat  more  prolonged  heating  of  the 
dry  residue  until  any  KC1O3  is  decomposed,  or  by  adding  a  little  sodium 
sulphite  to  the  solution  before  titration. 

The  granulated  lead  precipitates  the  Cu  as  metal.  The  lead  in  so- 
lution does  not  interfere  with  the  subsequent  titration. 

Volumetric  Determination  of  the  Zinc  —  Preparation  of 
the  Ferrocyanide  Solution. — Dissolve  forty-four  grms.  of  pure 
K4Fe  (CN)6  3  H2O  in  water  and  dilute  to  one  litre.  Ice  of 
this  will  precipitate  approximately  0.01  grm.  of  Zn. 

Standardize  the  solution  against  pure  zinc.  Dissolve  0.2  grms.  in 
lOcc  of  HC1,  add  seven  grms.  of  NH4C1,  dilute  to  lOOcc  and  heat  to  boiling. 
Now  run  in  the  ferrocyanide  solution  until  a  drop  of  the  liquid  shows  a 
brown  tinge  when  tested  on  a  white  plate  with  a  drop  of  a  strong  solu- 
tion of  uranic  nitrate  after  standing  two  or  three  minutes.  To  save 
time  make  several  such  tests  TVcc  apart,  and  take  the  reading  of  the  one 
showing  color  in  three  minutes.  Now  make  a  similar  test  upon  the 
HC1  -f-  NH4C1  without  the  zinc.  Deduct  the  amount  of  this  "  blank  " 
from  the  other,  and  the  difference  gives  the  amount  of  the  solution, 
equivalent  to  0.2  grms.  zinc. 

Determination  of  the  Zinc. — Titrate  the  strongly  acid 
solution  of  the  ore  exactly  as  above.  The  liquid  must  be 
boiling  hot. 

To  prevent  "  running  over"  it  is  a  good  plan  to  take  out  one-third 
of  the  liquid.  Titrate  the  remainder  roughly,  and  then  add  the  one- 
third  and  finish  carefully. 

Cadmium  when  present  counts  as  zinc  in  this  process. 

See  Jour.  An.  and  App.  Chem.,  vol   VI,  p.  491. 
Beringer,  Assaying,  p.  217. 


Notes  on  Metallurgical  Analysis.  93 

THE  ANALYSIS  OF  AI«L,OY8  OF  LEAD,  ABTTI- 
,  TIN   A>»    COPPER.      (BEARING 


Traces  of  As,  Fe  and  Zn  are  often  present.  The  complete  anal- 
ysis of  these  alloys  is  beyond  the  scope  of  these  notes,  hut  the  following 
method  for  the  determination  of  the  four  principal  metals  will  be  found 
satisfactory  if  carefully  conducted. 

The  most  troublesome  operations  are  the  separation  of  the  tin  from 
the  lead  and  from  the  antimony. 

See  Fresenius  Quant.  Anal.,  §  164,  also  §  165,  g  126  and  §  125. 

Process.  —  Weigh  0.5  grms.  of  the  fine  shavings  into  a  150cc  beaker. 
Add  two  grms.  of  solid  tartaric  acid  (powdered),  and  then  15cc  of 
HNO3,  1.2  sp.  gr.  Cover  and  warm  until  everything  is  dissolved,  wash 
off  and  remove  the  cover  and  evaporate  carefully  to  a  pasty  mass.  Now 
add  50cc  of  water  and  warm  until  all  the  lead  nitrate  has  dissolved.  The 
tin  and  antimony,  in  part,  are  left  as  a  fine  white  powder.  Now  drop 
in  a  cone,  solution  of  KHO  until  the  precipitate  formed  is  dissolved  in 
the  excess.  A  cloudiness  may  remain,  but  almost  all  will  go  into  solution. 
Add  lOcc  of  "yellow  sulphide  of  sodium  or  potassium,"  1  set  on  a  water 
bath  and  digest  at  a  temperature  considerably  short  of  boiling  for  three 
or  four  hours,  stirring  occasionally  and  keeping  the  beaker  covered.  Now 
decant  the  clear  liquid  through  a  filter,  and  wash  once  by  decantation. 
Avoid  getting  the  precipitate  on  the  filter,  but  decant  close  each  time. 
To  the  residue  add  lOcc  more  of  the  sulphide  solution,  but  no  water  and 
digest  again  for  two  hours.  Then  add  50cc  of  water  and  warm,  let  settle, 
decant,  transfer  and  wash  the  precipitate  with  H2S  water. 

The  Precipitate  contains  PbS  and  CuS.  Dry  the  filter  and  precip- 
itate ;  detach  the  latter  as  completely  as  possible  and  burn  the  filter  in 
a  small  porcelain  crucible  using  a  very  low  heat  and  merely  driving  off 
volatile  matter,  not  attempting  to  completely  burn  the  carbon.  Now 
add  the  burned  filter  to  the  rest  of  the  PbS  in  a  small  caserole.  Cover 
and  add  a  few  drops  of  cone.  HNO3  to  moisten  the  PbS  ;  then  add  5cc 
of  fuming  HNO3  (1.5  sp.  gr.).  Warm  for  some  time  and,  when  all  sul- 
phur has  disappeared,  add  5cc  of  H2SO4  (1  :  3)  and  evaporate  till  all 
HNO3  is  expelled.  Now  add  25cc  of  water  ;  stir  well,  let  settle,  filter 
and  wash  with  water  containing  about  \%  H2SO4,  and  finally  wash 
with  alcohol.  The  precipitate  is  PbSO4.  When  it  is  dry,  detach  it 
carefully  from  the  filter  and  put  in  a  small  weighed  porcelain  crucible. 
Burn  the  filter  paper  carefully  on  the  inverted  lid  of  the  crucible  and 

1.  Sulphide  of  Sodium  Solution.  —  This  is  made  by  saturating  a  20  per  cent,  solution  of  so- 
dium hydrate  with  H2S  gas.  Then  filter  the  solution  and  add  to  each  lOOcc  about  100  millegrammes 
of  flowers  of  sulphur.  This  will  dissolve  and  make  the  liquid  yellow.  This  solution  must  be 
kept  in  filled,  closely  stopped  bottles  and  used  fresh. 


94  Notes  on  Metallurgical  Analysis. 

add  to  the  ash  one  or  two  drops  of  cone.  HNO3  and  one  drop  of  H2SO4, 
evaporate  off  the  acids  carefully,  and  finally  dry  and  ignite  the  crucible 
and  cover  at  a  low  red  heat.  Now  weigh  all  together  and  determine  the 
PbSO4,  from  which  calculate  the  Pb. 

The  filtrate  from  the  PbSO4  contains  the  Cu.  This  may  be  precip- 
itated by  the  battery,  or  it  may  be  thrown  down  by  a  current  of  H2S, 
filtered  out,  washed  with  H2S  water,  dried,  ignited  and  weighed  as 
CuO  -f-  Cu2S.  (The  fact  that  the  weighed  precipitate  is  partially  con- 
verted to  oxide  by  the  air  is  unimportant,  as  the  per  cent,  of  Cu  in  CuO 
and  Cu2S  is  the  same). 

The  Solution  from  the  PbSand  C^tfcontains  the  Sb  and  Sn  (and  As) 
as  sulphides.  Dilute  the  liquid  to  about  250cc.  Add  HC1  carefully  until 
the  solution  distinctly  reddens  litmus,  but  avoid  much  excess,  set  on  a 
warm  plate  and  heat  gently  until  the  odor  of  H2S  has  nearly  gone. 

Filter  and  wash  once  by  decantation,  then  run  the  precipitate  on 
the  filter.  The  filtrate  will  grow  milky  in  time,  but  no  precipitate 
should  separate  from  it. 

The  precipitate,  consisting  of  Sb2S3,  SnS2  and  free  sulphur,  is  now 
washed  back  into  the  beaker,  using  a  wash  bottle  with  a  small  jet,  so  as 
to  accomplish  this  with  but  little  water.  With  care  the  amount  of  pre- 
cipitate left  on  the  filter  paper  will  be  but  trifling.  Now  dissolve  this 
off  through  the  filter  into  the  beaker  with  a  few  drops  of  a  dilute  solution 
of  NaHO ;  the  liquid  in  the  beaker  need  not  be  more  than  75cc.  Add 
to  the  contents  (water  and  sulphides)  10  to  15  grms.  of  solid  NaHO; 
when  this  is  dissolved,  add  carefully  about  3cc  of  bromine  (not  "  bromine 
water.")  Now  digest  on  a  water  bath  keeping  the  beaker  covered,  until 
the  sulphur  is  oxidized  or  collected  in  a  granular  form  and  the  antimony 
has  separated  as  a  white  crystalline  precipitate  of  sodium  metanti- 
moniate. 

Test  the  liquid  by  adding  to  a  drop  of  it  a  drop  or  two  of  HC1,  if  it 
gives  off  bromine  vapor  enough  Br.  has  been  added ;  if  not,  add  a  little 
more.  Finally  boil  the  liquid  a  few  minutes.  Now  cool  and  add  one-third 
the  volume  of  alcohol.  Let  stand  some  hours,  filter  and  wash  with  water 
containing  one-third  its  volume  of  alcohol  and  a  little  Na2 CO 3.  The 
filtrate  contains  all  the  SnO2  as  sodium  stannate,  and  the  precipitate 
contains  the  antimony  and  often  some  free  sulphur. 

Dilute  infiltrate  to  200cc,  add  HC1  until  it  is  distinctly  acid,  now 
warm  till  any  Br.  disappears,  and  then  add  200cc  of  H2S  water,  and 
pass  H2S  gas  till  saturated.  Let  stand  till  the  precipitate  settles,  filter 
and  wash  the  SnS2  thoroughly.  If  the  precipitate  tends  to  run  through 
the  filter,  add  ammonium  acetate  to  the  wash  water.  Put  the  filter  and 
precipitate  in  a  weighed  porcelain  crucible,  dry  and  burn  off  the  paper 
very  carefully,  finally  ignite  and  weigh  as  SnO2.  Addxa  little  solid  am- 
monium carbonate  to  the  crucible;  heat,  ignite  intensely  and  weigh 
again.  Any  loss  is  due  to  sulphuric  acid  held  by  the  SnO2. 


Notes  on  Metallurgical  Analysis.  95 

Ihe  Antimony  Precipitate  is  washed  back  into  the  beaker  and  dis- 
solved in  the  least  possible  amount  of  dilute  HC1,  containing  a  little  tar- 
taric  acid.  Wash  the  filter  with  the  same,  and  finally  filter  the  solution 
from  any  residual  sulphur.  (Which  will  be  free  from  antimony.) 

Now  dilute  to  about  250cc,  heat  to  nearly  boiling  and  pass  a  rapid 
current  of  H2S  till  the  Sb2S3  is  all  precipitated. 

Weigh  a  7  c.  m.  filter  paper,  as  in  the  phosphorus  determination 
by  the  yellow  precipitate  method.  Let  the  Sb2S3  precipitate  settle,  de- 
cant through  the  filter.  Transfer  the  precipitate,  wash  well  and  dry 
carefully  at  100°C  and  weigh  filter,  plus  precipitate.  This  gives  the 
total  weight  of  the  precipitate,  which  always  contains  free  sulphur. 
Now  detach  as  much  as  possible  from  the  filter  paper,  transfer  it  to  a 
weighed  porcelain  boat  and  weigh  the  boat  and  contents. 

Take  a  piece  of  combustion  tubing  large  enough  to  receive  the 
boat  and  its  contents  and  ten  or  twelve  inches  long.  Connect  one  end 
with  a  flask  for  generating  CO2  and  containing  fragments  of  marble. 
Close  the  other  end  of  the  combustion  tube  with  a  cork  containing  a 
small  exit  tube.  (There  must  be  a  U-tube  containing  CaCl2  between 
the  flask  and  the  combustion  tube  to  remove  moisture  from  the  gas.) 

Now  put  the  boat  and  its  contents  about  the  middle  of  the  tube, 
pour  a  little  dilute  HNO3  into  the  CO2  flask  and  let  the  current  of  gas 
pass  till  all  air  is  expelled  (four  or  five  minutes).  Now  carefully  heat 
the  tube  around  the  boat.  The  free  sulphur  volatilizes  and  the  Sb2S3 
turns  black  and  metallic  looking.  When  this  change  is  complete  and 
no  more  sulphur  vapors  pass  off',  cool  the  apparatus,  withdraw  the  boat 
and  weigh  it.  The  weight  of  the  contents  gives  the  pure  Sb2S3  in  the 
amount  taken. 

From  this  calculate  the  Sb2S3  in  the  total  precipitate  as  weighed 
originally,  and  from  this  again  the  Sb  in  the  sample. 

Notes  on  the  Above  Scheme. — The  use  of  the  tartaric  acid  is  to  assist 
the  solution  of  antimony,  which  is  but  slowly  oxidized  by  HNO3  alone. 
The  separation  of  tin  by  the  solubility  of  the  bisulphide  in  sodium  sul- 
phide is  complete,  provided  there  is  repeated  and  prolonged  digestion 
with  large  excess.  Sulphide  of  sodium  is  used  instead  of  sulphide  of 
ammonium  as  the  latter  dissolves  copper  sulphide.  In  the  treatment  of 
the  PbS  the  use  of  the  fuming  nitric  acid  causes  the  complete  oxidation 
of  the  sulphur.  With  ordinary  cone,  nitric  acid,  which  contains  about 
30%  of  water,  there  will  more  or  less  sulphur  separate  which  fuses  into 
globules.  When  the  PbSO4  is  ignited  this  melts  and  causes  reduction 
to  sulphide,  and  loss  of  weight. 

The  fuming  acid  can  be  most  easily  prepared  by  mixing  in  a  large 
retort  one  part  of  ordinary  HNO3  (C.  P.)  with  two  parts  of  cone. 
H2SO4  and  distilling  off  the  nitric  acid  into  a  cooled  dry  receiver.  The 
neck  of  the  retort  should  project  well  into  the  receiver. 


96  Notes  on  Metallurgical  Analysis. 

Arsenic,  if  present,  is  found  with  the  stannic  sulphide.  It  is  driven 
off  on  heating  the  SnO2. 

The  foregoing  method  for  the  separation  of  tin  and  antimony  de- 
pends upon  the  oxidation  of  the  Sb2S3  by  the  sodium  hypobromite  to 
sulphuric  acid  and  sodium  metantimoniate ;  the  usual  method  of  effect- 
ing this  is  by  fusion  with  sodium  hydrate  and  nitrate,  after  preliminary 
oxidation  by  HNO3.  The  wet  method  above  given  is  much  less  trouble- 
some and  equally  complete.  For  the  fusion  method  see  Fres.  Quant, 
loc.  cit. 

Clark's  method  of  separating  the  sulphides  by  oxalic  acid  is  also 
convenient  and  gives  excellent  results.  The  process  is  as  follows  : 

Wash  the  sulphides  into  a  beaker  as  before,  then  treat  them  with 
KC1O3  and  HC1.  Evaporate  to  dryness  and  add  tartaric  acid,  then  HC1 
and  water.  Filter  from  any  residue  of  sulphur.  Dilute  and  add  oxalic 
acid  in  large  excess  then  precipitate  by  H2S.  The  Sb2S3  comes  down, 
the  Sn  stays  in  solution.  The  precipitation  of  the  tin  in  the  filtrate  is  a 
matter  of  some  difficulty,  but  can  be  accomplished  if  the  excess  of  acid 
be  neutralized  and  the  solution  saturated  with  H2S,  made  ammoniacal, 
then  acidified  with  acetic  acid. 

See  Am.  Jour.  Sci.,  vol.  XLIX,  p.  154,  and  Am.  Ch«m.  Jour.,  vol.  I,  p.  244. 


XHK  EXAMINATION  OF  WAXBR  FOR  HOI  TICK 

SUPPLY. 

The  determination  of  the  "  scale-forming  ingredients  "  and  in  the 
case  of  water  contaminated  with  mine  drainage,  the  "acidity"  of  the 
water  is  all  that  is  necessary. 

Outline  Process  for  the  Analysis. — First,  evaporate  lOOcc  of  the  clear 
(if  necessary  filtered)  water  to  dryness  in  a  weighed  platinum  dish  and 
dry  at  100°  to  constant  weight.  This  gives  the  "  total  solids."  Second, 
test  the  water  for  chlorine.  If  any  considerable  amount  is  found  deter- 
mine it  volumetrically  with  a  standard  solution  of  AgNO3,  adding  a 
little  neutral  potassium  chromate  to  the  water  to  serve  as  an  indicator. 
The  slightest  excess  of  AgNO3  gives  the  reddish  color  due  to  silver 
chromate.  (See  Fresnius  Quant.,  §141.)  Third,  acidulate  one  litre  of 
the  water  with  a  little  HC1  and  evaporate  it  to  about  1 75cc.  Transfer 
it  to  a  200cc  flask  and  dilute  to  the  mark.  Take  of  this  lOOcc,  evaporate 
to  dryness  and  determine  the  silica,  iron  and  alumina,  the  CaO  and  the 
MgO  exactly  as  in  a  limestone.  Of  course  reducing  the  volumes  and 
amounts  of  reagents  to  correspond  to  the  smaller  quantity  taken.  Or 
the  evaporation  to  dryness  may  be  omitted  and  the  silica  will  then  come 
down  with  the  Fe2O3  and  may  be  so  included.  Take  50cc  and  deter- 
mine the  SO3  as  BaSO4  by  precipitation  with  BaCl2 .  (See  determination 
of  sulphur). 

Now  calculate  the  results  as  follows :    Combine  the  sulphuric  acid 


Notes  on  Metallurgical  A 


first  with  the  calcium.  All  calcium  left  over  is  to  be  estimated  as  carbon- 
ate. The  magnesium  is  to  be  combined  first  with  the  chlorine ;  next  with 
any  sulphuric  acid  left  from  the  calcium  and  lastly  the  residue  estimated 
as  carbonate. 

Should  the  water  contain  alkalies  in  any  amount,  this  will  be 
indicated  if  the  weight  of  the  "total  solids"  exceeds  by  any  consider- 
able amount  the  sum  of  the  sulphates,  carbonates  and  chlorides  of  cal- 
cium and  magnesium,  the  oxides  of  iron  and  alumina,  and  the  silica. 
They  may  be  determined  in  the  dry  residue  as  follows : 

Boil  the  residue  with  a  few  cc  of  water,  filter  and  wash.  Treat  the 
solution  first  with  an  excess  of  BaH2O2  solution  and  filter,  then  with 
ammonium  carbonate.  Filter  the  solution  from  the  precipitate  of 
BaCO3.  Evaporate  the  filtrate  and  expel  the  ammonium  salts  by  igni- 
tion. Determine  the  alkalies  in  the  residue  as  in  the  similar  residue  in 
the  analysis  of  fire  clays. 

In  computing  results  in  this  case,  first  combine  the  alkalies  with 
the  sulphuric  acid  and  chlorine,  proceeding  with  the  remainder  as 
before. 


APPENDIX. 


TABLE  OF  ATOMIC  WEIGHTS. 

The  following  table  comprises  the  atomic  weights  of  all  the  ele- 
ments of  usual  occurrence  or  of  special  interest  to  the  metallurgist. 

It  is  taken  from  one  published  by  the  U.  8.  Dep't.  of  Agriculture, 
and  revised  by  F.  W.  Clark,  Chief  Chemist  of  the  U.  S.  Geological 
Survey,  and  represents  the  most  trustworthy  results  up  to  1890. 


Name. 

Symbol. 

Atomic 
weight. 

Name. 

Symbol. 

Atomic 
weight. 

Aluminum  

Al 

27 

M^an  sra  n  e  se 

Mn 

fig 

Antimony  

Sb 

120 

Mercury     

He1 

200 

Arsenic    .  .       .... 

As 

75 

M^olvbdenum 

Mo 

9P> 

Barium  

Ba 

137 

Nickel 

ff\ 

58  7 

Bismuth  

Bi 

208  9 

Nitrojren 

N 

H()Q 

Boron  

B 

11 

Oxvsren 

Q 

16 

Bromine  

Br 

79  95 

Palladium 

Pd 

106  6 

Cadmium  

Cd 

112 

Phosphorus 

p 

31 

Calcium  

Ca 

40 

Platinum 

Pt 

195 

Carbon  

C 

12 

Potassium 

K 

39  11 

Chlorine  

Cl 

35  45 

Silicon 

Si 

28  4 

Chromium  

Cr 

52  1 

Silver 

Ao- 

107  92 

Cobalt  

Co 

59 

Sodium 

Na 

23  05 

Copper  

Cu 

63  6 

Strontium 

Sr 

87  6 

Fluoriu  

F 

19 

Sulphur 

S 

32  06 

Gold  

Au 

197  3 

Tin. 

Sn 

119 

Hydrogen  ......   . 

H 

1  007 

Titanium 

Ti 

48 

Iodine  

I 

126  85 

Tungsten 

W 

184 

Iron   

Fe 

56 

Uranium 

u 

239  6 

Lead  

Pb 

206  95 

Vanadium 

v 

51  4 

Li 

7  02 

Zinc  •  . 

Zn 

65  3 

Magnesium  

Mg 

24.3 

(98) 


Appendix. 
TABLE  OF  FACTOR  WEIGHTS. 


99 


The  following  I  nble  shows  the  amounts  of  material  to  be  taken 
that  each  millegram.  le  of  the  precipitate  weighed  may  equal  some 
definite  percentage  of  the  substance  sought : 


Substance  to  be 
determined. 

Precipitate  to  be 
weighed. 

Amount  of  the 
substance   to   be 
determined  in 
the    precipitate 
weighed. 

Factor  weights  to 
be  taken. 

Per  cent,  of  the 
substance  to  be  de- 
termined  repre- 
sented by  each  mil- 
legramme  of  pre- 
cipitate. 

s 

BaS04 

0.1373 

1.373 

0.01 

S03 

BaS04, 

0.3433 

1.716 

0.02 

Si 

810, 

0.4667 

1.167 

0.04 

p 

Mg2P207 

0.2790 

2.790 

0.01 

P2O  = 

Mg2P207 

0.6396 

2.198 

0.03 

Mn 

Mn3O4 

0.7200 

1.440 

0.05 

Mn 

Mn2P2O7 

0.3873 

0.387 

0.10 

C 

C02 

0.2727 

2.727 

0.01 

APPLYING  THE   "  CORRECTION    FACTORS"     OF    VOLUMETRIC    SOLUTIONS 
TO  THE  AMOUNTS  OF  SUBSTANCE  TAKEN. 

This  method  of  avoiding  calculation  in  obtaining  the  results  of 
volumetric  analyses  is  frequently  very  convenient. 

It  has  been  indicated  in  the  notes  on  the  iodine  method  for  sulphur. 

In  general  where  a  solution  is  made  up  so  that  each  cubic  centi- 
meter shall  represent  a  definite  per  cent,  of  some  constituent  when  a 
certain  weight  of  substance  is  taken  for  the  analysis  ;  if  on  standardiz- 
ing the  solution  each  c  c  is  found  to  be  in  fact  equivalent  to  some  fraction 
of  that  value,  the  usual  plan  is  to  multiply  all  results  by  that  fraction 
to  get  the  true  results. 

If,  however,  the  assumed  amount  of  substance  be  multiplied  by 
that  same  fraction  (or  factor),  and  the  resulting  amount  actually  used 
in  the  analysis,  the  number  of  cubic  centimeters  taken  will  give  the  true 
percentages  at  once. 

Thus  in  the  Eminerton  phosphorus  method  when  1  c  c  of  the  per- 
manganate is  calculated  to  be  equal  to  0.002  per  cent,  of  P  if  five  grms. 
of  iron  are  taken,  suppose  that  on  standardizing  10.3  cc  of  the  solution 
were  found  equivalent  to  what  10  c  c  should  be. 

Then  Ice  would  be  equivalent  to  ^  of  .002  per  cent,  on  five  grms. 
taken,  JL  being  the  "factor."  In  this  case  by  "weighing  out"  5 

XJQ^  grms.  (4.854),  the  number  of  c  cs  used,  multiplied  by  .002,  will  give 
the  percentage. 


100  Appendix. 

SOMK  ADDITIONAL  1VOTBS  AND  METHODS. 

1.      SAMPLING  SPIEGEL  IRON   AND   WHITE   CAST   IRON. 

These  and  similar  materials  which  are  too  hard  to  drill  must  be 
broken  into  small  fragments  with  a  sledge  hammer  and  several  pieces 
pulverized  in  a  steel  mortar.  A  very  efficient  mortar  for  this  purpose 
can  be  made  by  boring  an  inch  hole  two  inches  deep  into  a  block  of 
tool  steel  about  three  inches  square  and  four  inches  high.  Fit  this  with 
a  steel  "rammer"  cut  from  a  round  bar  and  about  three  inches  longer 
than  the  hole.  It  must  be  only  slightly  smaller  than  the  hole  in  the 
block.  Both  block  and  rammer  must  be  well  hardened.  By  dropping 
a  fragment  of  metal  into  the  hole,  inserting  the  rammer  and  pounding 
it  vigorously  with  a  heavy  hammer  the  hardest  material  is  soon  re- 
duced to  a  fine  sand. 

2.      THE   DETERMINATION   OF   IRON  IN  ORES   BY    PERMANGANATE. 

The  following  very  rapid  method  is  used  on  Lake  Superior  ores : 

(See  Eng.  and  Min.  Jour.,  Vol.  LVII,  No.  15.) 

Take  about  0.5  grm.  of  ore,  add  2£  c  c  of  SnCl2  solution  and  10  to  15 
c  c  of  HC1  (1:1).  Boil  gently  until  the  iron  is  all  dissolved.  This  is  easily 
seen  owing  to  the  light  color  of  the  solution,  the  SnCl2  reducing  the 
iron  to  the  ferrous  form.  Now,  if  necessary,  drop  in  more  tin  solution 
to  complete  the  reduction  and  then  add  5  c  c  of  a  saturated  solution  of 
HgCl2  to  remove  the  excess  of  SnCl2.  Dilute  the  solution  to  about 
250  c  c,  add  5  or  10  cc  of  "  titrating  solution,"  then  add  standard  perman- 
ganate solution  until  the  last  drop  gives  a  persistent  pink  color. 

The  "titrating  solution"  is  made  by  dissolving  160  grms.  of  man- 
ganous  sulphate  in  water,  diluting  to  1750  c  c  and  adding  330  c  c  of  phos- 
phoric acid  and  320  c  c  of  sulphuric  acid. 

The  standard  permanganate  solution  is  calculated  so  that  each 
cubic  centimeter  shall  represent  2  per  cent,  of  iron  when  0.5  grm.  of  ore 
is  taken.  Its  exact  value  is  then  determined  by  testing  against  a 
known  ore  or  pure  iron,  and  then  the  amount  of  ore  taken  in  the  anal- 
ysis so  varied  that  each  c  c  of  the  actual  solution  still  represents  2  per 
cent.  The  addition  of  the  SuCl2  during  solution  reduces  the  time  re- 
quired. The  sulphate  of  manganese  in  the  "titrating  solution"  pre- 
vents the  reduction  of  permanganate  by  the  HC1  present.  The  process 
would  have  to  be  used  with  caution,  as  the  presence  of  organic  matter 
or  other  reducing  agents  in  the  ore  would  render  the  results  inaccurate. 

3.      ON   DIFFICULTY   IN   FILTERING   SOLUTIONS  OF   PIG   IRON  AND  STEEL 
IN   PHOSPHORUS  DETERMINATIONS. 

When  pig  iron  or  steel  high  in  silicon  is  dissolved  in  HNO3  and 
after  evaporation  and  "baking"  the  residue  dissolved  in  HC1,  the  solu- 
tion obtained  will  be  found  very  slow  in  filtering  owing  to  the  presence 
of  SiO2  in  a  peculiarly  gelatinous  form. 


Appendix.  101 

The  SiO2  left  after  the  evaporation  of  an  HC1  solution  is  much 
more  granular  and  easily  filtered  off.  Therefore,  in  all  cases  where  sil- 
icon is  present  to  any  extent  the  HC1  solution  of  the  baked  residue  must 
be  evaporated  to  dryness  again  and  then  redissolved  in  HC1.  This  sec- 
ond evaporation  takes  but  little  time,  and  is  essential  when  using  a 
process  like  that  of  Emmerton  or  Wood  on  cast  iron,  if  a  long  and 
tedious  nitration  is  to  be  avoided. 

It  is  stated  that  the  addition  of  a  few  drops  of  HF  or  a  little 
NH4F  to  the  first  HC1  solution  will  also  cause  it  to  filter  more  rapidly 
and  render  the  second  evaporation  unnecessary. 

4.      THE  PURIFICATION   OF   BARIUM  SULPHATE. 

When  a  precipitate  of  BaSO4  is  colored  red  by  iron,  as  is  sometimes 
the  case  in  sulphur  determinations  when  the  solution  was  too  hot  or  con- 
tained too  little  free  acid,  it  can  be  easily  purified  by  solution  in  con- 
centrated H2SO4.  Add  to  the  precipitate  in  the  crucible  2  or  3  c  c  of  con- 
centrated H2SO4  and  heat  till  solution  is  complete.  Cool  and  pour  into 
100  c  c  of  cold  water,  washing  out  the  crucible.  The  BaSO4  separates  im- 
mediately and  can  be  filtered  off,  washed  a  little,  ignited  and  weighed. 
The  results  are,  however,  liable  to  be  too  low,  not  from  the  failure  to  re- 
cover all  the  BaSO4,  but  because  the  red  precipitate  may  contain  basic 
iron  sulphate. 

5.      ON  THE  PRESENCE  OF   NITRITES  IN  CAUSTIC  ALKALIES  AS  A  SOURCE 
OF   ERROR  IN  SULPHUR  AND   CARBON  DETERMINATIONS. 

Commercial  caustic  potassa  sometimes  contains  nitrites.  The  effect 
of  these  on  the  volumetric  sulphur  process  is  to  liberate  iodine  from  the 
KI  in  the  solution,  and  so  vitiate  the  results.  Their  presence  is  not 
shown  by  the  ordinary  "  blank"  test  with  starch  and  iodine  solution. 

To  test  the  potash  solution  add  HC1  until  acid,  then  starch  paste 
and  a  little  pure  KI;  if  a  blue  color  develops,  a  nitrite  or  some  sim- 
ilar compound  is  present  and  the  solution  cannot  be  used.  These  and 
other  oxygen  absorbents  like  FeO,  when  present  in  caustic  potassa  and 
soda,  also  cause  trouble  in  the  "carbon  train,"  giving  rise  to  constant 
gain  in  weight  in  the  potash  bulbs  during  aspirating.  The  difficulty 
may  be  overcome  by  adding  permanganate  of  potassa  to  the  boiling 
alkali  solution  drop  by  drop  until  a  faint,  persistent  green  color  is  pro- 
duced. Let  the  liquid  cool  and  settle  and  decant  the  clear  solution. 


ERRATA. 

Page  14,  line  3,  for  CaH2O2,  read  MgH2O2. 

Page  14,  line  30,  for  CaC4O4,  read  CaC2O4. 

Page  15,  line  13,  for  Fe2Cl4,  read  Fe2Cl6. 

Page  16,  line  33,  for  basis,  read  basic. 

Page  20,  line  5,  for  130  Cy,  read  130°C. 

Page  20,  line  5,  for  12  MoO3PO4  (NH4)3,  read  12  MoO3,  PO4 
(NH4)3. 

Page  32,  line  26,  for  20 : 11  =  .0001  :  x,  read  n  :  20  =  .0001  :  x. 

1  ige  33,  line  19,  for  HNO4,  read  HNO3. 

Page  35,  line  4  from  bottom,  for  one-fourth,  read  one. 

Page  40,  line  17,  for  now  dilute  to  150cc  and  add  NH4HO  till  a  slight 
permanent  precipitate  is  formed,  then  a  few  drops  of  acetic  acid  and 
boil.  Read  now  dilute  to  150  cc,  add  NH4HO  till  just  alkaline,  then 
acetic  acid  drop  by  drop  till  just  acid,  and  boil. 

Page  41,  line  6,  for  drillings,  read  powdered  metal. 

Page  41,  line  6,  for  dissolve  in  10  c  c  HNO3 1.2  sp.  gr.  evaporate— read 
dissolve  in  10  c  c  HNO3  1.2  sp.  gr.  and  5  c  c  HC1  evaporate— 

Page  52,  line  25,  for  add  5  c  c  cone.  HC1,  read  add  5  to  10  c  c  cone.  HC1. 

Page  52,  line  31,  for  now  heat,  read  now  warm  to  about  60°. 

Page  57,  line  14,  for  Na?.S2O3  5  H2O,  read  2  Na2S2O3  5  H2O. 

Page  72  to  references  on  color  TiO2,  add  Dunniugton  Jour.  Am. 
Chem.  Soc.,  XIII,  No.  7. 

Page  84,  line  6,  for  warmed,  but  not  boiled,  read  boiled  for  2  or  3 
minutes. 

Page  85,  line  27,  for  warmed,  read  boiled. 

Page  87,  line  12,  for  now  filter  and  wash  with  hot  water  until  the 
filtrate  is  free  from  Cl,  read  now  filter  and  wash  with  hot  water  until 
the  filtrate  amounts  to  about  250  c  c.  This  will  extract  all  the  alkalies. 


(102) 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  5O  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


;    APU   111937 

$P^     *>£4    Vj'/b 

!A      9    19^'j 

"^  18  '^38 

22(V*'61NT 

'      ^ 

OPJ-  g 

LD  21-100m-8,'34 

•VC  63400 


